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diff --git a/doc/rfc/rfc3951.txt b/doc/rfc/rfc3951.txt new file mode 100644 index 0000000..d4fba08 --- /dev/null +++ b/doc/rfc/rfc3951.txt @@ -0,0 +1,10867 @@ + + + + + + +Network Working Group S. Andersen +Request for Comments: 3951 Aalborg University +Category: Experimental A. Duric + Telio + H. Astrom + R. Hagen + W. Kleijn + J. Linden + Global IP Sound + December 2004 + + + Internet Low Bit Rate Codec (iLBC) + +Status of this Memo + + This memo defines an Experimental Protocol for the Internet + community. It does not specify an Internet standard of any kind. + Discussion and suggestions for improvement are requested. + Distribution of this memo is unlimited. + +Copyright Notice + + Copyright (C) The Internet Society (2004). + +Abstract + + This document specifies a speech codec suitable for robust voice + communication over IP. The codec is developed by Global IP Sound + (GIPS). It is designed for narrow band speech and results in a + payload bit rate of 13.33 kbit/s for 30 ms frames and 15.20 kbit/s + for 20 ms frames. The codec enables graceful speech quality + degradation in the case of lost frames, which occurs in connection + with lost or delayed IP packets. + + + + + + + + + + + + + + + + + +Andersen, et al. Experimental [Page 1] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + +Table of Contents + + 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 + 2. Outline of the Codec . . . . . . . . . . . . . . . . . . . . . 5 + 2.1. Encoder. . . . . . . . . . . . . . . . . . . . . . . . . 5 + 2.2. Decoder. . . . . . . . . . . . . . . . . . . . . . . . . 7 + 3. Encoder Principles . . . . . . . . . . . . . . . . . . . . . . 7 + 3.1. Pre-processing . . . . . . . . . . . . . . . . . . . . . 9 + 3.2. LPC Analysis and Quantization. . . . . . . . . . . . . . 9 + 3.2.1. Computation of Autocorrelation Coefficients. . . 10 + 3.2.2. Computation of LPC Coefficients. . . . . . . . . 11 + 3.2.3. Computation of LSF Coefficients from LPC + Coefficients . . . . . . . . . . . . . . . . . . 11 + 3.2.4. Quantization of LSF Coefficients . . . . . . . . 12 + 3.2.5. Stability Check of LSF Coefficients. . . . . . . 13 + 3.2.6. Interpolation of LSF Coefficients. . . . . . . . 13 + 3.2.7. LPC Analysis and Quantization for 20 ms Frames . 14 + 3.3. Calculation of the Residual. . . . . . . . . . . . . . . 15 + 3.4. Perceptual Weighting Filter. . . . . . . . . . . . . . . 15 + 3.5. Start State Encoder. . . . . . . . . . . . . . . . . . . 15 + 3.5.1. Start State Estimation . . . . . . . . . . . . . 16 + 3.5.2. All-Pass Filtering and Scale Quantization. . . . 17 + 3.5.3. Scalar Quantization. . . . . . . . . . . . . . . 18 + 3.6. Encoding the Remaining Samples . . . . . . . . . . . . . 19 + 3.6.1. Codebook Memory. . . . . . . . . . . . . . . . . 20 + 3.6.2. Perceptual Weighting of Codebook Memory + and Target . . . . . . . . . . . . . . . . . . . 22 + 3.6.3. Codebook Creation. . . . . . . . . . . . . . . . 23 + 3.6.3.1. Creation of a Base Codebook . . . . . . 23 + 3.6.3.2. Codebook Expansion. . . . . . . . . . . 24 + 3.6.3.3. Codebook Augmentation . . . . . . . . . 24 + 3.6.4. Codebook Search. . . . . . . . . . . . . . . . . 26 + 3.6.4.1. Codebook Search at Each Stage . . . . . 26 + 3.6.4.2. Gain Quantization at Each Stage . . . . 27 + 3.6.4.3. Preparation of Target for Next Stage. . 28 + 3.7. Gain Correction Encoding . . . . . . . . . . . . . . . . 28 + 3.8. Bitstream Definition . . . . . . . . . . . . . . . . . . 29 + 4. Decoder Principles . . . . . . . . . . . . . . . . . . . . . . 32 + 4.1. LPC Filter Reconstruction. . . . . . . . . . . . . . . . 33 + 4.2. Start State Reconstruction . . . . . . . . . . . . . . . 33 + 4.3. Excitation Decoding Loop . . . . . . . . . . . . . . . . 34 + 4.4. Multistage Adaptive Codebook Decoding. . . . . . . . . . 35 + 4.4.1. Construction of the Decoded Excitation Signal. . 35 + 4.5. Packet Loss Concealment. . . . . . . . . . . . . . . . . 35 + 4.5.1. Block Received Correctly and Previous Block + Also Received. . . . . . . . . . . . . . . . . . 35 + 4.5.2. Block Not Received . . . . . . . . . . . . . . . 36 + + + + +Andersen, et al. Experimental [Page 2] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + 4.5.3. Block Received Correctly When Previous Block + Not Received . . . . . . . . . . . . . . . . . . 36 + 4.6. Enhancement. . . . . . . . . . . . . . . . . . . . . . . 37 + 4.6.1. Estimating the Pitch . . . . . . . . . . . . . . 39 + 4.6.2. Determination of the Pitch-Synchronous + Sequences. . . . . . . . . . . . . . . . . . . . 39 + 4.6.3. Calculation of the Smoothed Excitation . . . . . 41 + 4.6.4. Enhancer Criterion . . . . . . . . . . . . . . . 41 + 4.6.5. Enhancing the Excitation . . . . . . . . . . . . 42 + 4.7. Synthesis Filtering. . . . . . . . . . . . . . . . . . . 43 + 4.8. Post Filtering . . . . . . . . . . . . . . . . . . . . . 43 + 5. Security Considerations. . . . . . . . . . . . . . . . . . . . 43 + 6. Evaluation of the iLBC Implementations . . . . . . . . . . . . 43 + 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 43 + 7.1. Normative References . . . . . . . . . . . . . . . . . . 43 + 7.2. Informative References . . . . . . . . . . . . . . . . . 44 + 8. ACKNOWLEDGEMENTS . . . . . . . . . . . . . . . . . . . . . . . 44 + APPENDIX A: Reference Implementation . . . . . . . . . . . . . . . 45 + A.1. iLBC_test.c. . . . . . . . . . . . . . . . . . . . . . . 46 + A.2 iLBC_encode.h. . . . . . . . . . . . . . . . . . . . . . 52 + A.3. iLBC_encode.c. . . . . . . . . . . . . . . . . . . . . . 53 + A.4. iLBC_decode.h. . . . . . . . . . . . . . . . . . . . . . 63 + A.5. iLBC_decode.c. . . . . . . . . . . . . . . . . . . . . . 64 + A.6. iLBC_define.h. . . . . . . . . . . . . . . . . . . . . . 76 + A.7. constants.h. . . . . . . . . . . . . . . . . . . . . . . 80 + A.8. constants.c. . . . . . . . . . . . . . . . . . . . . . . 82 + A.9. anaFilter.h. . . . . . . . . . . . . . . . . . . . . . . 96 + A.10. anaFilter.c. . . . . . . . . . . . . . . . . . . . . . . 97 + A.11. createCB.h . . . . . . . . . . . . . . . . . . . . . . . 98 + A.12. createCB.c . . . . . . . . . . . . . . . . . . . . . . . 99 + A.13. doCPLC.h . . . . . . . . . . . . . . . . . . . . . . . .104 + A.14. doCPLC.c . . . . . . . . . . . . . . . . . . . . . . . .104 + A.15. enhancer.h . . . . . . . . . . . . . . . . . . . . . . .109 + A.16. enhancer.c . . . . . . . . . . . . . . . . . . . . . . .110 + A.17. filter.h . . . . . . . . . . . . . . . . . . . . . . . .123 + A.18. filter.c . . . . . . . . . . . . . . . . . . . . . . . .125 + A.19. FrameClassify.h. . . . . . . . . . . . . . . . . . . . .128 + A.20. FrameClassify.c. . . . . . . . . . . . . . . . . . . . .129 + A.21. gainquant.h. . . . . . . . . . . . . . . . . . . . . . .131 + A.22. gainquant.c. . . . . . . . . . . . . . . . . . . . . . .131 + A.23. getCBvec.h . . . . . . . . . . . . . . . . . . . . . . .134 + A.24. getCBvec.c . . . . . . . . . . . . . . . . . . . . . . .134 + A.25. helpfun.h. . . . . . . . . . . . . . . . . . . . . . . .138 + A.26. helpfun.c. . . . . . . . . . . . . . . . . . . . . . . .140 + A.27. hpInput.h. . . . . . . . . . . . . . . . . . . . . . . .146 + A.28. hpInput.c. . . . . . . . . . . . . . . . . . . . . . . .146 + A.29. hpOutput.h . . . . . . . . . . . . . . . . . . . . . . .148 + A.30. hpOutput.c . . . . . . . . . . . . . . . . . . . . . . .148 + + + +Andersen, et al. Experimental [Page 3] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + A.31. iCBConstruct.h . . . . . . . . . . . . . . . . . . . . .149 + A.32. iCBConstruct.c . . . . . . . . . . . . . . . . . . . . .150 + A.33. iCBSearch.h. . . . . . . . . . . . . . . . . . . . . . .152 + A.34. iCBSearch.c. . . . . . . . . . . . . . . . . . . . . . .153 + A.35. LPCdecode.h. . . . . . . . . . . . . . . . . . . . . . .163 + A.36. LPCdecode.c. . . . . . . . . . . . . . . . . . . . . . .164 + A.37. LPCencode.h. . . . . . . . . . . . . . . . . . . . . . .167 + A.38. LPCencode.c. . . . . . . . . . . . . . . . . . . . . . .167 + A.39. lsf.h. . . . . . . . . . . . . . . . . . . . . . . . . .172 + A.40. lsf.c. . . . . . . . . . . . . . . . . . . . . . . . . .172 + A.41. packing.h. . . . . . . . . . . . . . . . . . . . . . . .178 + A.42. packing.c. . . . . . . . . . . . . . . . . . . . . . . .179 + A.43. StateConstructW.h. . . . . . . . . . . . . . . . . . . .182 + A.44. StateConstructW.c. . . . . . . . . . . . . . . . . . . .183 + A.45. StateSearchW.h . . . . . . . . . . . . . . . . . . . . .185 + A.46. StateSearchW.c . . . . . . . . . . . . . . . . . . . . .186 + A.47. syntFilter.h . . . . . . . . . . . . . . . . . . . . . .190 + A.48. syntFilter.c . . . . . . . . . . . . . . . . . . . . . .190 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . .192 + Full Copyright Statement . . . . . . . . . . . . . . . . . . . . .194 + +1. Introduction + + This document contains the description of an algorithm for the coding + of speech signals sampled at 8 kHz. The algorithm, called iLBC, uses + a block-independent linear-predictive coding (LPC) algorithm and has + support for two basic frame lengths: 20 ms at 15.2 kbit/s and 30 ms + at 13.33 kbit/s. When the codec operates at block lengths of 20 ms, + it produces 304 bits per block, which SHOULD be packetized as in [1]. + Similarly, for block lengths of 30 ms it produces 400 bits per block, + which SHOULD be packetized as in [1]. The two modes for the + different frame sizes operate in a very similar way. When they + differ it is explicitly stated in the text, usually with the notation + x/y, where x refers to the 20 ms mode and y refers to the 30 ms mode. + + The described algorithm results in a speech coding system with a + controlled response to packet losses similar to what is known from + pulse code modulation (PCM) with packet loss concealment (PLC), such + as the ITU-T G.711 standard [4], which operates at a fixed bit rate + of 64 kbit/s. At the same time, the described algorithm enables + fixed bit rate coding with a quality-versus-bit rate tradeoff close + to state-of-the-art. A suitable RTP payload format for the iLBC + codec is specified in [1]. + + Some of the applications for which this coder is suitable are real + time communications such as telephony and videoconferencing, + streaming audio, archival, and messaging. + + + + +Andersen, et al. Experimental [Page 4] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + Cable Television Laboratories (CableLabs(R)) has adopted iLBC as a + mandatory PacketCable(TM) audio codec standard for VoIP over Cable + applications [3]. + + This document is organized as follows. Section 2 gives a brief + outline of the codec. The specific encoder and decoder algorithms + are explained in sections 3 and 4, respectively. Appendix A provides + a c-code reference implementation. + + The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", + "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this + document are to be interpreted as described in BCP 14, RFC 2119 [2]. + +2. Outline of the Codec + + The codec consists of an encoder and a decoder as described in + sections 2.1 and 2.2, respectively. + + The essence of the codec is LPC and block-based coding of the LPC + residual signal. For each 160/240 (20 ms/30 ms) sample block, the + following major steps are performed: A set of LPC filters are + computed, and the speech signal is filtered through them to produce + the residual signal. The codec uses scalar quantization of the + dominant part, in terms of energy, of the residual signal for the + block. The dominant state is of length 57/58 (20 ms/30 ms) samples + and forms a start state for dynamic codebooks constructed from the + already coded parts of the residual signal. These dynamic codebooks + are used to code the remaining parts of the residual signal. By this + method, coding independence between blocks is achieved, resulting in + elimination of propagation of perceptual degradations due to packet + loss. The method facilitates high-quality packet loss concealment + (PLC). + +2.1. Encoder + + The input to the encoder SHOULD be 16 bit uniform PCM sampled at 8 + kHz. It SHOULD be partitioned into blocks of BLOCKL=160/240 samples + for the 20/30 ms frame size. Each block is divided into NSUB=4/6 + consecutive sub-blocks of SUBL=40 samples each. For 30 ms frame + size, the encoder performs two LPC_FILTERORDER=10 linear-predictive + coding (LPC) analyses. The first analysis applies a smooth window + centered over the second sub-block and extending to the middle of the + fifth sub-block. The second LPC analysis applies a smooth asymmetric + window centered over the fifth sub-block and extending to the end of + the sixth sub-block. For 20 ms frame size, one LPC_FILTERORDER=10 + linear-predictive coding (LPC) analysis is performed with a smooth + window centered over the third sub-frame. + + + + +Andersen, et al. Experimental [Page 5] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + For each of the LPC analyses, a set of line-spectral frequencies + (LSFs) are obtained, quantized, and interpolated to obtain LSF + coefficients for each sub-block. Subsequently, the LPC residual is + computed by using the quantized and interpolated LPC analysis + filters. + + The two consecutive sub-blocks of the residual exhibiting the maximal + weighted energy are identified. Within these two sub-blocks, the + start state (segment) is selected from two choices: the first 57/58 + samples or the last 57/58 samples of the two consecutive sub-blocks. + The selected segment is the one of higher energy. The start state is + encoded with scalar quantization. + + A dynamic codebook encoding procedure is used to encode 1) the 23/22 + (20 ms/30 ms) remaining samples in the two sub-blocks containing the + start state; 2) the sub-blocks after the start state in time; and 3) + the sub-blocks before the start state in time. Thus, the encoding + target can be either the 23/22 samples remaining of the two sub- + blocks containing the start state or a 40-sample sub-block. This + target can consist of samples indexed forward in time or backward in + time, depending on the location of the start state. + + The codebook coding is based on an adaptive codebook built from a + codebook memory that contains decoded LPC excitation samples from the + already encoded part of the block. These samples are indexed in the + same time direction as the target vector, ending at the sample + instant prior to the first sample instant represented in the target + vector. The codebook is used in CB_NSTAGES=3 stages in a successive + refinement approach, and the resulting three code vector gains are + encoded with 5-, 4-, and 3-bit scalar quantization, respectively. + + The codebook search method employs noise shaping derived from the LPC + filters, and the main decision criterion is to minimize the squared + error between the target vector and the code vectors. Each code + vector in this codebook comes from one of CB_EXPAND=2 codebook + sections. The first section is filled with delayed, already encoded + residual vectors. The code vectors of the second codebook section + are constructed by predefined linear combinations of vectors in the + first section of the codebook. + + As codebook encoding with squared-error matching is known to produce + a coded signal of less power than does the scalar quantized start + state signal, a gain re-scaling method is implemented by a refined + search for a better set of codebook gains in terms of power matching + after encoding. This is done by searching for a higher value of the + gain factor for the first stage codebook, as the subsequent stage + codebook gains are scaled by the first stage gain. + + + + +Andersen, et al. Experimental [Page 6] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + +2.2. Decoder + + Typically for packet communications, a jitter buffer placed at the + receiving end decides whether the packet containing an encoded signal + block has been received or lost. This logic is not part of the codec + described here. For each encoded signal block received the decoder + performs a decoding. For each lost signal block, the decoder + performs a PLC operation. + + The decoding for each block starts by decoding and interpolating the + LPC coefficients. Subsequently the start state is decoded. + + For codebook-encoded segments, each segment is decoded by + constructing the three code vectors given by the received codebook + indices in the same way that the code vectors were constructed in the + encoder. The three gain factors are also decoded and the resulting + decoded signal is given by the sum of the three codebook vectors + scaled with respective gain. + + An enhancement algorithm is applied to the reconstructed excitation + signal. This enhancement augments the periodicity of voiced speech + regions. The enhancement is optimized under the constraint that the + modification signal (defined as the difference between the enhanced + excitation and the excitation signal prior to enhancement) has a + short-time energy that does not exceed a preset fraction of the + short-time energy of the excitation signal prior to enhancement. + + A packet loss concealment (PLC) operation is easily embedded in the + decoder. The PLC operation can, e.g., be based on repeating LPC + filters and obtaining the LPC residual signal by using a long-term + prediction estimate from previous residual blocks. + +3. Encoder Principles + + The following block diagram is an overview of all the components of + the iLBC encoding procedure. The description of the blocks contains + references to the section where that particular procedure is further + described. + + + + + + + + + + + + + +Andersen, et al. Experimental [Page 7] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + +-----------+ +---------+ +---------+ + speech -> | 1. Pre P | -> | 2. LPC | -> | 3. Ana | -> + +-----------+ +---------+ +---------+ + + +---------------+ +--------------+ + -> | 4. Start Sel | ->| 5. Scalar Qu | -> + +---------------+ +--------------+ + + +--------------+ +---------------+ + -> |6. CB Search | -> | 7. Packetize | -> payload + | +--------------+ | +---------------+ + ----<---------<------ + sub-frame 0..2/4 (20 ms/30 ms) + + Figure 3.1. Flow chart of the iLBC encoder + + 1. Pre-process speech with a HP filter, if needed (section 3.1). + + 2. Compute LPC parameters, quantize, and interpolate (section 3.2). + + 3. Use analysis filters on speech to compute residual (section 3.3). + + 4. Select position of 57/58-sample start state (section 3.5). + + 5. Quantize the 57/58-sample start state with scalar quantization + (section 3.5). + + 6. Search the codebook for each sub-frame. Start with 23/22 sample + block, then encode sub-blocks forward in time, and then encode + sub-blocks backward in time. For each block, the steps in Figure + 3.4 are performed (section 3.6). + + 7. Packetize the bits into the payload specified in Table 3.2. + + The input to the encoder SHOULD be 16-bit uniform PCM sampled at 8 + kHz. Also it SHOULD be partitioned into blocks of BLOCKL=160/240 + samples. Each block input to the encoder is divided into NSUB=4/6 + consecutive sub-blocks of SUBL=40 samples each. + + + + + + + + + + + + + +Andersen, et al. Experimental [Page 8] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + 0 39 79 119 159 + +---------------------------------------+ + | 1 | 2 | 3 | 4 | + +---------------------------------------+ + 20 ms frame + + 0 39 79 119 159 199 239 + +-----------------------------------------------------------+ + | 1 | 2 | 3 | 4 | 5 | 6 | + +-----------------------------------------------------------+ + 30 ms frame + Figure 3.2. One input block to the encoder for 20 ms (with four sub- + frames) and 30 ms (with six sub-frames). + +3.1. Pre-processing + + In some applications, the recorded speech signal contains DC level + and/or 50/60 Hz noise. If these components have not been removed + prior to the encoder call, they should be removed by a high-pass + filter. A reference implementation of this, using a filter with a + cutoff frequency of 90 Hz, can be found in Appendix A.28. + +3.2. LPC Analysis and Quantization + + The input to the LPC analysis module is a possibly high-pass filtered + speech buffer, speech_hp, that contains 240/300 (LPC_LOOKBACK + + BLOCKL = 80/60 + 160/240 = 240/300) speech samples, where samples 0 + through 79/59 are from the previous block and samples 80/60 through + 239/299 are from the current block. No look-ahead into the next + block is used. For the very first block processed, the look-back + samples are assumed to be zeros. + + For each input block, the LPC analysis calculates one/two set(s) of + LPC_FILTERORDER=10 LPC filter coefficients using the autocorrelation + method and the Levinson-Durbin recursion. These coefficients are + converted to the Line Spectrum Frequency representation. In the 20 + ms case, the single lsf set represents the spectral characteristics + as measured at the center of the third sub-block. For 30 ms frames, + the first set, lsf1, represents the spectral properties of the input + signal at the center of the second sub-block, and the other set, + lsf2, represents the spectral characteristics as measured at the + center of the fifth sub-block. The details of the computation for 30 + ms frames are described in sections 3.2.1 through 3.2.6. Section + 3.2.7 explains how the LPC Analysis and Quantization differs for 20 + ms frames. + + + + + + +Andersen, et al. Experimental [Page 9] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + +3.2.1. Computation of Autocorrelation Coefficients + + The first step in the LPC analysis procedure is to calculate + autocorrelation coefficients by using windowed speech samples. This + windowing is the only difference in the LPC analysis procedure for + the two sets of coefficients. For the first set, a 240-sample-long + standard symmetric Hanning window is applied to samples 0 through 239 + of the input data. The first window, lpc_winTbl, is defined as + + lpc_winTbl[i]= 0.5 * (1.0 - cos((2*PI*(i+1))/(BLOCKL+1))); + i=0,...,119 + lpc_winTbl[i] = winTbl[BLOCKL - i - 1]; i=120,...,239 + + The windowed speech speech_hp_win1 is then obtained by multiplying + the first 240 samples of the input speech buffer with the window + coefficients: + + speech_hp_win1[i] = speech_hp[i] * lpc_winTbl[i]; + i=0,...,BLOCKL-1 + + From these 240 windowed speech samples, 11 (LPC_FILTERORDER + 1) + autocorrelation coefficients, acf1, are calculated: + + acf1[lag] += speech_hp_win1[n] * speech_hp_win1[n + lag]; + lag=0,...,LPC_FILTERORDER; n=0,...,BLOCKL-lag-1 + + In order to make the analysis more robust against numerical precision + problems, a spectral smoothing procedure is applied by windowing the + autocorrelation coefficients before the LPC coefficients are + computed. Also, a white noise floor is added to the autocorrelation + function by multiplying coefficient zero by 1.0001 (40dB below the + energy of the windowed speech signal). These two steps are + implemented by multiplying the autocorrelation coefficients with the + following window: + + lpc_lagwinTbl[0] = 1.0001; + lpc_lagwinTbl[i] = exp(-0.5 * ((2 * PI * 60.0 * i) /FS)^2); + i=1,...,LPC_FILTERORDER + where FS=8000 is the sampling frequency + + Then, the windowed acf function acf1_win is obtained by + + acf1_win[i] = acf1[i] * lpc_lagwinTbl[i]; + i=0,...,LPC_FILTERORDER + + The second set of autocorrelation coefficients, acf2_win, are + obtained in a similar manner. The window, lpc_asymwinTbl, is applied + to samples 60 through 299, i.e., the entire current block. The + + + +Andersen, et al. Experimental [Page 10] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + window consists of two segments, the first (samples 0 to 219) being + half a Hanning window with length 440 and the second a quarter of a + cycle of a cosine wave. By using this asymmetric window, an LPC + analysis centered in the fifth sub-block is obtained without the need + for any look-ahead, which would add delay. The asymmetric window is + defined as + + lpc_asymwinTbl[i] = (sin(PI * (i + 1) / 441))^2; i=0,...,219 + + lpc_asymwinTbl[i] = cos((i - 220) * PI / 40); i=220,...,239 + + and the windowed speech is computed by + + speech_hp_win2[i] = speech_hp[i + LPC_LOOKBACK] * + lpc_asymwinTbl[i]; i=0,....BLOCKL-1 + + The windowed autocorrelation coefficients are then obtained in + exactly the same way as for the first analysis instance. + + The generation of the windows lpc_winTbl, lpc_asymwinTbl, and + lpc_lagwinTbl are typically done in advance, and the arrays are + stored in ROM rather than repeating the calculation for every block. + +3.2.2. Computation of LPC Coefficients + + From the 2 x 11 smoothed autocorrelation coefficients, acf1_win and + acf2_win, the 2 x 11 LPC coefficients, lp1 and lp2, are calculated + in the same way for both analysis locations by using the well known + Levinson-Durbin recursion. The first LPC coefficient is always 1.0, + resulting in ten unique coefficients. + + After determining the LPC coefficients, a bandwidth expansion + procedure is applied to smooth the spectral peaks in the + short-term spectrum. The bandwidth addition is obtained by the + following modification of the LPC coefficients: + + lp1_bw[i] = lp1[i] * chirp^i; i=0,...,LPC_FILTERORDER + lp2_bw[i] = lp2[i] * chirp^i; i=0,...,LPC_FILTERORDER + + where "chirp" is a real number between 0 and 1. It is RECOMMENDED to + use a value of 0.9. + +3.2.3. Computation of LSF Coefficients from LPC Coefficients + + Thus far, two sets of LPC coefficients that represent the short-term + spectral characteristics of the speech signal for two different time + locations within the current block have been determined. These + coefficients SHOULD be quantized and interpolated. Before this is + + + +Andersen, et al. Experimental [Page 11] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + done, it is advantageous to convert the LPC parameters into another + type of representation called Line Spectral Frequencies (LSF). The + LSF parameters are used because they are better suited for + quantization and interpolation than the regular LPC coefficients. + Many computationally efficient methods for calculating the LSFs from + the LPC coefficients have been proposed in the literature. The + detailed implementation of one applicable method can be found in + Appendix A.26. The two arrays of LSF coefficients obtained, lsf1 and + lsf2, are of dimension 10 (LPC_FILTERORDER). + +3.2.4. Quantization of LSF Coefficients + + Because the LPC filters defined by the two sets of LSFs are also + needed in the decoder, the LSF parameters need to be quantized and + transmitted as side information. The total number of bits required + to represent the quantization of the two LSF representations for one + block of speech is 40, with 20 bits used for each of lsf1 and lsf2. + + For computational and storage reasons, the LSF vectors are quantized + using three-split vector quantization (VQ). That is, the LSF vectors + are split into three sub-vectors that are each quantized with a + regular VQ. The quantized versions of lsf1 and lsf2, qlsf1 and + qlsf2, are obtained by using the same memoryless split VQ. The + length of each of these two LSF vectors is 10, and they are split + into three sub-vectors containing 3, 3, and 4 values, respectively. + + For each of the sub-vectors, a separate codebook of quantized values + has been designed with a standard VQ training method for a large + database containing speech from a large number of speakers recorded + under various conditions. The size of each of the three codebooks + associated with the split definitions above is + + int size_lsfCbTbl[LSF_NSPLIT] = {64,128,128}; + + The actual values of the vector quantization codebook that must be + used can be found in the reference code of Appendix A. Both sets of + LSF coefficients, lsf1 and lsf2, are quantized with a standard + memoryless split vector quantization (VQ) structure using the squared + error criterion in the LSF domain. The split VQ quantization + consists of the following steps: + + 1) Quantize the first three LSF coefficients (1 - 3) with a VQ + codebook of size 64. + 2) Quantize the next three LSF coefficients 4 - 6 with VQ a codebook + of size 128. + 3) Quantize the last four LSF coefficients (7 - 10) with a VQ + codebook of size 128. + + + + +Andersen, et al. Experimental [Page 12] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + This procedure, repeated for lsf1 and lsf2, gives six quantization + indices and the quantized sets of LSF coefficients qlsf1 and qlsf2. + Each set of three indices is encoded with 6 + 7 + 7 = 20 bits. The + total number of bits used for LSF quantization in a block is thus 40 + bits. + +3.2.5. Stability Check of LSF Coefficients + + The LSF representation of the LPC filter has the convenient property + that the coefficients are ordered by increasing value, i.e., lsf(n-1) + < lsf(n), 0 < n < 10, if the corresponding synthesis filter is + stable. As we are employing a split VQ scheme, it is possible that + at the split boundaries the LSF coefficients are not ordered + correctly and hence that the corresponding LP filter is unstable. To + ensure that the filter used is stable, a stability check is performed + for the quantized LSF vectors. If it turns out that the coefficients + are not ordered appropriately (with a safety margin of 50 Hz to + ensure that formant peaks are not too narrow), they will be moved + apart. The detailed method for this can be found in Appendix A.40. + The same procedure is performed in the decoder. This ensures that + exactly the same LSF representations are used in both encoder and + decoder. + +3.2.6. Interpolation of LSF Coefficients + + From the two sets of LSF coefficients that are computed for each + block of speech, different LSFs are obtained for each sub-block by + means of interpolation. This procedure is performed for the original + LSFs (lsf1 and lsf2), as well as the quantized versions qlsf1 and + qlsf2, as both versions are used in the encoder. Here follows a + brief summary of the interpolation scheme; the details are found in + the c-code of Appendix A. In the first sub-block, the average of the + second LSF vector from the previous block and the first LSF vector in + the current block is used. For sub-blocks two through five, the LSFs + used are obtained by linear interpolation from lsf1 (and qlsf1) to + lsf2 (and qlsf2), with lsf1 used in sub-block two and lsf2 in sub- + block five. In the last sub-block, lsf2 is used. For the very first + block it is assumed that the last LSF vector of the previous block is + equal to a predefined vector, lsfmeanTbl, obtained by calculating the + mean LSF vector of the LSF design database. + + lsfmeanTbl[LPC_FILTERORDER] = {0.281738, 0.445801, 0.663330, + 0.962524, 1.251831, 1.533081, 1.850586, 2.137817, + 2.481445, 2.777344} + + + + + + + +Andersen, et al. Experimental [Page 13] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + The interpolation method is standard linear interpolation in the LSF + domain. The interpolated LSF values are converted to LPC + coefficients for each sub-block. The unquantized and quantized LPC + coefficients form two sets of filters respectively. The unquantized + analysis filter for sub-block k is defined as follows + + ___ + \ + Ak(z)= 1 + > ak(i)*z^(-i) + /__ + i=1...LPC_FILTERORDER + + The quantized analysis filter for sub-block k is defined as follows + ___ + \ + A~k(z)= 1 + > a~k(i)*z^(-i) + /__ + i=1...LPC_FILTERORDER + + A reference implementation of the lsf encoding is given in Appendix + A.38. A reference implementation of the corresponding decoding can + be found in Appendix A.36. + +3.2.7. LPC Analysis and Quantization for 20 ms Frames + + As previously stated, the codec only calculates one set of LPC + parameters for the 20 ms frame size as opposed to two sets for 30 ms + frames. A single set of autocorrelation coefficients is calculated + on the LPC_LOOKBACK + BLOCKL = 80 + 160 = 240 samples. These samples + are windowed with the asymmetric window lpc_asymwinTbl, centered over + the third sub-frame, to form speech_hp_win. Autocorrelation + coefficients, acf, are calculated on the 240 samples in speech_hp_win + and then windowed exactly as in section 3.2.1 (resulting in + acf_win). + + This single set of windowed autocorrelation coefficients is used to + calculate LPC coefficients, LSF coefficients, and quantized LSF + coefficients in exactly the same manner as in sections 3.2.3 through + 3.2.4. As for the 30 ms frame size, the ten LSF coefficients are + divided into three sub-vectors of size 3, 3, and 4 and quantized by + using the same scheme and codebook as in section 3.2.4 to finally get + 3 quantization indices. The quantized LSF coefficients are + stabilized with the algorithm described in section 3.2.5. + + From the set of LSF coefficients computed for this block and those + from the previous block, different LSFs are obtained for each sub- + block by means of interpolation. The interpolation is done linearly + in the LSF domain over the four sub-blocks, so that the n-th sub- + + + +Andersen, et al. Experimental [Page 14] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + frame uses the weight (4-n)/4 for the LSF from old frame and the + weight n/4 of the LSF from the current frame. For the very first + block the mean LSF, lsfmeanTbl, is used as the LSF from the previous + block. Similarly as seen in section 3.2.6, both unquantized, A(z), + and quantized, A~(z), analysis filters are calculated for each of the + four sub-blocks. + +3.3. Calculation of the Residual + + The block of speech samples is filtered by the quantized and + interpolated LPC analysis filters to yield the residual signal. In + particular, the corresponding LPC analysis filter for each 40 sample + sub-block is used to filter the speech samples for the same sub- + block. The filter memory at the end of each sub-block is carried + over to the LPC filter of the next sub-block. The signal at the + output of each LP analysis filter constitutes the residual signal for + the corresponding sub-block. + + A reference implementation of the LPC analysis filters is given in + Appendix A.10. + +3.4. Perceptual Weighting Filter + + In principle any good design of a perceptual weighting filter can be + applied in the encoder without compromising this codec definition. + However, it is RECOMMENDED to use the perceptual weighting filter Wk + for sub-block k specified below: + + Wk(z)=1/Ak(z/LPC_CHIRP_WEIGHTDENUM), where + LPC_CHIRP_WEIGHTDENUM = 0.4222 + + This is a simple design with low complexity that is applied in the + LPC residual domain. Here Ak(z) is the filter obtained for sub-block + k from unquantized but interpolated LSF coefficients. + +3.5. Start State Encoder + + The start state is quantized by using a common 6-bit scalar quantizer + for the block and a 3-bit scalar quantizer operating on scaled + samples in the weighted speech domain. In the following we describe + the state encoding in greater detail. + + + + + + + + + + +Andersen, et al. Experimental [Page 15] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + +3.5.1. Start State Estimation + + The two sub-blocks containing the start state are determined by + finding the two consecutive sub-blocks in the block having the + highest power. Advantageously, down-weighting is used in the + beginning and end of the sub-frames, i.e., the following measure is + computed (NSUB=4/6 for 20/30 ms frame size): + + nsub=1,...,NSUB-1 + ssqn[nsub] = 0.0; + for (i=(nsub-1)*SUBL; i<(nsub-1)*SUBL+5; i++) + ssqn[nsub] += sampEn_win[i-(nsub-1)*SUBL]* + residual[i]*residual[i]; + for (i=(nsub-1)*SUBL+5; i<(nsub+1)*SUBL-5; i++) + ssqn[nsub] += residual[i]*residual[i]; + for (i=(nsub+1)*SUBL-5; i<(nsub+1)*SUBL; i++) + ssqn[nsub] += sampEn_win[(nsub+1)*SUBL-i-1]* + residual[i]*residual[i]; + + where sampEn_win[5]={1/6, 2/6, 3/6, 4/6, 5/6}; MAY be used. The + sub-frame number corresponding to the maximum value of + ssqEn_win[nsub-1]*ssqn[nsub] is selected as the start state + indicator. A weighting of ssqEn_win[]={0.8,0.9,1.0,0.9,0.8} for 30 + ms frames and ssqEn_win[]={0.9,1.0,0.9} for 20 ms frames; MAY + advantageously be used to bias the start state towards the middle of + the frame. + + For 20 ms frames there are three possible positions for the two-sub- + block length maximum power segment; the start state position is + encoded with 2 bits. The start state position, start, MUST be + encoded as + + start=1: start state in sub-frame 0 and 1 + start=2: start state in sub-frame 1 and 2 + start=3: start state in sub-frame 2 and 3 + + For 30 ms frames there are five possible positions of the two-sub- + block length maximum power segment, the start state position is + encoded with 3 bits. The start state position, start, MUST be + encoded as + + start=1: start state in sub-frame 0 and 1 + start=2: start state in sub-frame 1 and 2 + start=3: start state in sub-frame 2 and 3 + start=4: start state in sub-frame 3 and 4 + start=5: start state in sub-frame 4 and 5 + + + + + +Andersen, et al. Experimental [Page 16] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + Hence, in both cases, index 0 is not used. In order to shorten the + start state for bit rate efficiency, the start state is brought down + to STATE_SHORT_LEN=57 samples for 20 ms frames and STATE_SHORT_LEN=58 + samples for 30 ms frames. The power of the first 23/22 and last + 23/22 samples of the two sub-frame blocks identified above is + computed as the sum of the squared signal sample values, and the + 23/22-sample segment with the lowest power is excluded from the start + state. One bit is transmitted to indicate which of the two possible + 57/58 sample segments is used. The start state position within the + two sub-frames determined above, state_first, MUST be encoded as + + state_first=1: start state is first STATE_SHORT_LEN samples + state_first=0: start state is last STATE_SHORT_LEN samples + +3.5.2. All-Pass Filtering and Scale Quantization + + The block of residual samples in the start state is first filtered by + an all-pass filter with the quantized LPC coefficients as denominator + and reversed quantized LPC coefficients as numerator. The purpose of + this phase-dispersion filter is to get a more even distribution of + the sample values in the residual signal. The filtering is performed + by circular convolution, where the initial filter memory is set to + zero. + + res(0..(STATE_SHORT_LEN-1)) = uncoded start state residual + res((STATE_SHORT_LEN)..(2*STATE_SHORT_LEN-1)) = 0 + + Pk(z) = A~rk(z)/A~k(z), where + ___ + \ + A~rk(z)= z^(-LPC_FILTERORDER)+>a~k(i+1)*z^(i-(LPC_FILTERORDER-1)) + /__ + i=0...(LPC_FILTERORDER-1) + + and A~k(z) is taken from the block where the start state begins + + res -> Pk(z) -> filtered + + ccres(k) = filtered(k) + filtered(k+STATE_SHORT_LEN), + k=0..(STATE_SHORT_LEN-1) + + The all-pass filtered block is searched for its largest magnitude + sample. The 10-logarithm of this magnitude is quantized with a 6-bit + quantizer, state_frgqTbl, by finding the nearest representation. + + + + + + + +Andersen, et al. Experimental [Page 17] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + This results in an index, idxForMax, corresponding to a quantized + value, qmax. The all-pass filtered residual samples in the block are + then multiplied with a scaling factor scal=4.5/(10^qmax) to yield + normalized samples. + + state_frgqTbl[64] = {1.000085, 1.071695, 1.140395, 1.206868, + 1.277188, 1.351503, 1.429380, 1.500727, 1.569049, + 1.639599, 1.707071, 1.781531, 1.840799, 1.901550, + 1.956695, 2.006750, 2.055474, 2.102787, 2.142819, + 2.183592, 2.217962, 2.257177, 2.295739, 2.332967, + 2.369248, 2.402792, 2.435080, 2.468598, 2.503394, + 2.539284, 2.572944, 2.605036, 2.636331, 2.668939, + 2.698780, 2.729101, 2.759786, 2.789834, 2.818679, + 2.848074, 2.877470, 2.906899, 2.936655, 2.967804, + 3.000115, 3.033367, 3.066355, 3.104231, 3.141499, + 3.183012, 3.222952, 3.265433, 3.308441, 3.350823, + 3.395275, 3.442793, 3.490801, 3.542514, 3.604064, + 3.666050, 3.740994, 3.830749, 3.938770, 4.101764} + +3.5.3. Scalar Quantization + + The normalized samples are quantized in the perceptually weighted + speech domain by a sample-by-sample scalar DPCM quantization as + depicted in Figure 3.3. Each sample in the block is filtered by a + weighting filter Wk(z), specified in section 3.4, to form a weighted + speech sample x[n]. The target sample d[n] is formed by subtracting + a predicted sample y[n], where the prediction filter is given by + + Pk(z) = 1 - 1 / Wk(z). + + +-------+ x[n] + d[n] +-----------+ u[n] + residual -->| Wk(z) |-------->(+)---->| Quantizer |------> quantized + +-------+ - /|\ +-----------+ | residual + | \|/ + y[n] +--------------------->(+) + | | + | +------+ | + +--------| Pk(z)|<------+ + +------+ + + Figure 3.3. Quantization of start state samples by DPCM in weighted + speech domain. + + The coded state sample u[n] is obtained by quantizing d[n] with a 3- + bit quantizer with quantization table state_sq3Tbl. + + state_sq3Tbl[8] = {-3.719849, -2.177490, -1.130005, -0.309692, + 0.444214, 1.329712, 2.436279, 3.983887} + + + +Andersen, et al. Experimental [Page 18] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + The quantized samples are transformed back to the residual domain by + 1) scaling with 1/scal; 2) time-reversing the scaled samples; 3) + filtering the time-reversed samples by the same all-pass filter, as + in section 3.5.2, by using circular convolution; and 4) time- + reversing the filtered samples. (More detail is in section 4.2.) + + A reference implementation of the start-state encoding can be found + in Appendix A.46. + +3.6. Encoding the Remaining Samples + + A dynamic codebook is used to encode 1) the 23/22 remaining samples + in the two sub-blocks containing the start state; 2) the sub-blocks + after the start state in time; and 3) the sub-blocks before the start + state in time. Thus, the encoding target can be either the 23/22 + samples remaining of the 2 sub-blocks containing the start state, or + a 40-sample sub-block. This target can consist of samples that are + indexed forward in time or backward in time, depending on the + location of the start state. The length of the target is denoted by + lTarget. + + The coding is based on an adaptive codebook that is built from a + codebook memory that contains decoded LPC excitation samples from the + already encoded part of the block. These samples are indexed in the + same time direction as is the target vector and end at the sample + instant prior to the first sample instant represented in the target + vector. The codebook memory has length lMem, which is equal to + CB_MEML=147 for the two/four 40-sample sub-blocks and 85 for the + 23/22-sample sub-block. + + The following figure shows an overview of the encoding procedure. + + +------------+ +---------------+ +-------------+ + -> | 1. Decode | -> | 2. Mem setup | -> | 3. Perc. W. | -> + +------------+ +---------------+ +-------------+ + + +------------+ +-----------------+ + -> | 4. Search | -> | 5. Upd. Target | ------------------> + | +------------+ +------------------ | + ----<-------------<-----------<---------- + stage=0..2 + + +----------------+ + -> | 6. Recalc G[0] | ---------------> gains and CB indices + +----------------+ + + Figure 3.4. Flow chart of the codebook search in the iLBC encoder. + + + + +Andersen, et al. Experimental [Page 19] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + 1. Decode the part of the residual that has been encoded so far, + using the codebook without perceptual weighting. + + 2. Set up the memory by taking data from the decoded residual. This + memory is used to construct codebooks. For blocks preceding the + start state, both the decoded residual and the target are time + reversed (section 3.6.1). + 3. Filter the memory + target with the perceptual weighting filter + (section 3.6.2). + + 4. Search for the best match between the target and the codebook + vector. Compute the optimal gain for this match and quantize that + gain (section 3.6.4). + + 5. Update the perceptually weighted target by subtracting the + contribution from the selected codebook vector from the + perceptually weighted memory (quantized gain times selected + vector). Repeat 4 and 5 for the two additional stages. + + 6. Calculate the energy loss due to encoding of the residual. If + needed, compensate for this loss by an upscaling and + requantization of the gain for the first stage (section 3.7). + + The following sections provide an in-depth description of the + different blocks of Figure 3.4. + +3.6.1. Codebook Memory + + The codebook memory is based on the already encoded sub-blocks, so + the available data for encoding increases for each new sub-block that + has been encoded. Until enough sub-blocks have been encoded to fill + the codebook memory with data, it is padded with zeros. The + following figure shows an example of the order in which the sub- + blocks are encoded for the 30 ms frame size if the start state is + located in the last 58 samples of sub-block 2 and 3. + + +-----------------------------------------------------+ + | 5 | 1 |///|////////| 2 | 3 | 4 | + +-----------------------------------------------------+ + + Figure 3.5. The order from 1 to 5 in which the sub-blocks are + encoded. The slashed area is the start state. + + + + + + + + + +Andersen, et al. Experimental [Page 20] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + The first target sub-block to be encoded is number 1, and the + corresponding codebook memory is shown in the following figure. As + the target vector comes before the start state in time, the codebook + memory and target vector are time reversed; thus, after the block has + been time reversed the search algorithm can be reused. As only the + start state has been encoded so far, the last samples of the codebook + memory are padded with zeros. + + +------------------------- + |zeros|\\\\\\\\|\\\\| 1 | + +------------------------- + + Figure 3.6. The codebook memory, length lMem=85 samples, and the + target vector 1, length 22 samples. + + The next step is to encode sub-block 2 by using the memory that now + has increased since sub-block 1 has been encoded. The following + figure shows the codebook memory for encoding of sub-block 2. + + +----------------------------------- + | zeros | 1 |///|////////| 2 | + +----------------------------------- + + Figure 3.7. The codebook memory, length lMem=147 samples, and the + target vector 2, length 40 samples. + + The next step is to encode sub-block 3 by using the memory which has + been increased yet again since sub-blocks 1 and 2 have been encoded, + but the sub-block still has to be padded with a few zeros. The + following figure shows the codebook memory for encoding of sub-block + 3. + + +------------------------------------------ + |zeros| 1 |///|////////| 2 | 3 | + +------------------------------------------ + + Figure 3.8. The codebook memory, length lMem=147 samples, and the + target vector 3, length 40 samples. + + The next step is to encode sub-block 4 by using the memory which now + has increased yet again since sub-blocks 1, 2, and 3 have been + encoded. This time, the memory does not have to be padded with + zeros. The following figure shows the codebook memory for encoding + of sub-block 4. + + + + + + + +Andersen, et al. Experimental [Page 21] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + +------------------------------------------ + |1|///|////////| 2 | 3 | 4 | + +------------------------------------------ + + Figure 3.9. The codebook memory, length lMem=147 samples, and the + target vector 4, length 40 samples. + + The final target sub-block to be encoded is number 5, and the + following figure shows the corresponding codebook memory. As the + target vector comes before the start state in time, the codebook + memory and target vector are time reversed. + + +------------------------------------------- + | 3 | 2 |\\\\\\\\|\\\\| 1 | 5 | + +------------------------------------------- + + Figure 3.10. The codebook memory, length lMem=147 samples, and the + target vector 5, length 40 samples. + + For the case of 20 ms frames, the encoding procedure looks almost + exactly the same. The only difference is that the size of the start + state is 57 samples and that there are only three sub-blocks to be + encoded. The encoding order is the same as above, starting with the + 23-sample target and then encoding the two remaining 40-sample sub- + blocks, first going forward in time and then going backward in time + relative to the start state. + +3.6.2. Perceptual Weighting of Codebook Memory and Target + + To provide a perceptual weighting of the coding error, a + concatenation of the codebook memory and the target to be coded is + all-pole filtered with the perceptual weighting filter specified in + section 3.4. The filter state of the weighting filter is set to + zero. + + in(0..(lMem-1)) = unweighted codebook memory + in(lMem..(lMem+lTarget-1)) = unweighted target signal + + + in -> Wk(z) -> filtered, + where Wk(z) is taken from the sub-block of the target + + weighted codebook memory = filtered(0..(lMem-1)) + weighted target signal = filtered(lMem..(lMem+lTarget-1)) + + The codebook search is done with the weighted codebook memory and the + weighted target, whereas the decoding and the codebook memory update + uses the unweighted codebook memory. + + + +Andersen, et al. Experimental [Page 22] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + +3.6.3. Codebook Creation + + The codebook for the search is created from the perceptually weighted + codebook memory. It consists of two sections, where the first is + referred to as the base codebook and the second as the expanded + codebook, as it is created by linear combinations of the first. Each + of these two sections also has a subsection referred to as the + augmented codebook. The augmented codebook is only created and used + for the coding of the 40-sample sub-blocks and not for the 23/22- + sample sub-block case. The codebook size used for the different + sub-blocks and different stages are summarized in the table below. + + Stage + 1 2 & 3 + -------------------------------------------- + 22 128 (64+0)*2 128 (64+0)*2 + Sub- 1:st 40 256 (108+20)*2 128 (44+20)*2 + Blocks 2:nd 40 256 (108+20)*2 256 (108+20)*2 + 3:rd 40 256 (108+20)*2 256 (108+20)*2 + 4:th 40 256 (108+20)*2 256 (108+20)*2 + + Table 3.1. Codebook sizes for the 30 ms mode. + + Table 3.1 shows the codebook size for the different sub-blocks and + stages for 30 ms frames. Inside the parentheses it shows how the + number of codebook vectors is distributed, within the two sections, + between the base/expanded codebook and the augmented base/expanded + codebook. It should be interpreted in the following way: + (base/expanded cb + augmented base/expanded cb). The total number of + codebook vectors for a specific sub-block and stage is given by the + following formula: + + Tot. cb vectors = base cb + aug. base cb + exp. cb + aug. exp. cb + + The corresponding values to Figure 3.1 for 20 ms frames are only + slightly modified. The short sub-block is 23 instead of 22 samples, + and the 3:rd and 4:th sub-frame are not present. + +3.6.3.1. Creation of a Base Codebook + + The base codebook is given by the perceptually weighted codebook + memory that is mentioned in section 3.5.3. The different codebook + vectors are given by sliding a window of length 23/22 or 40, given by + variable lTarget, over the lMem-long perceptually weighted codebook + memory. The indices are ordered so that the codebook vector + containing sample (lMem-lTarget-n) to (lMem-n-1) of the codebook + + + + + +Andersen, et al. Experimental [Page 23] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + memory vector has index n, where n=0..lMem-lTarget. Thus the total + number of base codebook vectors is lMem-lTarget+1, and the indices + are ordered from sample delay lTarget (23/22 or 40) to lMem+1 (86 or + 148). + +3.6.3.2. Codebook Expansion + + The base codebook is expanded by a factor of 2, creating an + additional section in the codebook. This new section is obtained by + filtering the base codebook, base_cb, with a FIR filter with filter + length CB_FILTERLEN=8. The construction of the expanded codebook + compensates for the delay of four samples introduced by the FIR + filter. + + cbfiltersTbl[CB_FILTERLEN]={-0.033691, 0.083740, -0.144043, + 0.713379, 0.806152, -0.184326, + 0.108887, -0.034180}; + + ___ + \ + exp_cb(k)= + > cbfiltersTbl(i)*x(k-i+4) + /__ + i=0...(LPC_FILTERORDER-1) + + where x(j) = base_cb(j) for j=0..lMem-1 and 0 otherwise + + The individual codebook vectors of the new filtered codebook, exp_cb, + and their indices are obtained in the same fashion as described above + for the base codebook. + +3.6.3.3. Codebook Augmentation + + For cases where encoding entire sub-blocks, i.e., cbveclen=40, the + base and expanded codebooks are augmented to increase codebook + richness. The codebooks are augmented by vectors produced by + interpolation of segments. The base and expanded codebook, + constructed above, consists of vectors corresponding to sample delays + in the range from cbveclen to lMem. The codebook augmentation + attempts to augment these codebooks with vectors corresponding to + sample delays from 20 to 39. However, not all of these samples are + present in the base codebook and expanded codebook, respectively. + Therefore, the augmentation vectors are constructed as linear + combinations between samples corresponding to sample delays in the + range 20 to 39. The general idea of this procedure is presented in + the following figures and text. The procedure is performed for both + the base codebook and the expanded codebook. + + + + + +Andersen, et al. Experimental [Page 24] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + - - ------------------------| + codebook memory | + - - ------------------------| + |-5-|---15---|-5-| + pi pp po + + | | Codebook vector + |---15---|-5-|-----20-----| <- corresponding to + i ii iii sample delay 20 + + Figure 3.11. Generation of the first augmented codebook. + + Figure 3.11 shows the codebook memory with pointers pi, pp, and po, + where pi points to sample 25, pp to sample 20, and po to sample 5. + Below the codebook memory, the augmented codebook vector + corresponding to sample delay 20 is drawn. Segment i consists of + fifteen samples from pointer pp and forward in time. Segment ii + consists of five interpolated samples from pi and forward and from po + and forward. The samples are linearly interpolated with weights + [0.0, 0.2, 0.4, 0.6, 0.8] for pi and weights [1.0, 0.8, 0.6, 0.4, + 0.2] for po. Segment iii consists of twenty samples from pp and + forward. The augmented codebook vector corresponding to sample delay + 21 is produced by moving pointers pp and pi one sample backward in + time. This gives us the following figure. + + - - ------------------------| + codebook memory | + - - ------------------------| + |-5-|---16---|-5-| + pi pp po + + | | Codebook vector + |---16---|-5-|-----19-----| <- corresponding to + i ii iii sample delay 21 + + Figure 3.12. Generation of the second augmented codebook. + + Figure 3.12 shows the codebook memory with pointers pi, pp and po + where pi points to sample 26, pp to sample 21, and po to sample 5. + Below the codebook memory, the augmented codebook vector + corresponding to sample delay 21 is drawn. Segment i now consists of + sixteen samples from pp and forward. Segment ii consists of five + interpolated samples from pi and forward and from po and forward, and + the interpolation weights are the same throughout the procedure. + Segment iii consists of nineteen samples from pp and forward. The + same procedure of moving the two pointers is continued until the last + augmented vector corresponding to sample delay 39 has been created. + This gives a total of twenty new codebook vectors to each of the two + + + +Andersen, et al. Experimental [Page 25] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + sections. Thus the total number of codebook vectors for each of the + two sections, when including the augmented codebook, becomes lMem- + SUBL+1+SUBL/2. This is provided that augmentation is evoked, i.e., + that lTarget=SUBL. + +3.6.4. Codebook Search + + The codebook search uses the codebooks described in the sections + above to find the best match of the perceptually weighted target, see + section 3.6.2. The search method is a multi-stage gain-shape + matching performed as follows. At each stage the best shape vector + is identified, then the gain is calculated and quantized, and finally + the target is updated in preparation for the next codebook search + stage. The number of stages is CB_NSTAGES=3. + + If the target is the 23/22-sample vector the codebooks are indexed so + that the base codebook is followed by the expanded codebook. If the + target is 40 samples the order is as follows: base codebook, + augmented base codebook, expanded codebook, and augmented expanded + codebook. The size of each codebook section and its corresponding + augmented section is given by Table 3.1 in section 3.6.3. + + For example, when the second 40-sample sub-block is coded, indices 0 + - 107 correspond to the base codebook, 108 - 127 correspond to the + augmented base codebook, 128 - 235 correspond to the expanded + codebook, and indices 236 - 255 correspond to the augmented expanded + codebook. The indices are divided in the same fashion for all stages + in the example. Only in the case of coding the first 40-sample sub- + block is there a difference between stages (see Table 3.1). + +3.6.4.1. Codebook Search at Each Stage + + The codebooks are searched to find the best match to the target at + each stage. When the best match is found, the target is updated and + the next-stage search is started. The three chosen codebook vectors + and their corresponding gains constitute the encoded sub-block. The + best match is decided by the following three criteria: + + 1. Compute the measure + + (target*cbvec)^2 / ||cbvec||^2 + + for all codebook vectors, cbvec, and choose the codebook vector + maximizing the measure. The expression (target*cbvec) is the dot + product between the target vector to be coded and the codebook vector + for which we compute the measure. The norm, ||x||, is defined as the + square root of (x*x). + + + + +Andersen, et al. Experimental [Page 26] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + 2. The absolute value of the gain, corresponding to the chosen + codebook vector, cbvec, must be smaller than a fixed limit, + CB_MAXGAIN=1.3: + + |gain| < CB_MAXGAIN + + where the gain is computed in the following way: + + gain = (target*cbvec) / ||cbvec||^2 + + 3. For the first stage, the dot product of the chosen codebook vector + and target must be positive: + + target*cbvec > 0 + + In practice the above criteria are used in a sequential search + through all codebook vectors. The best match is found by registering + a new max measure and index whenever the previously registered max + measure is surpassed and all other criteria are fulfilled. If none + of the codebook vectors fulfill (2) and (3), the first codebook + vector is selected. + +3.6.4.2. Gain Quantization at Each Stage + + The gain follows as a result of the computation + + gain = (target*cbvec) / ||cbvec||^2 + + for the optimal codebook vector found by the procedure in section + 3.6.4.1. + + The three stages quantize the gain, using 5, 4, and 3 bits, + respectively. In the first stage, the gain is limited to positive + values. This gain is quantized by finding the nearest value in the + quantization table gain_sq5Tbl. + + gain_sq5Tbl[32]={0.037476, 0.075012, 0.112488, 0.150024, 0.187500, + 0.224976, 0.262512, 0.299988, 0.337524, 0.375000, + 0.412476, 0.450012, 0.487488, 0.525024, 0.562500, + 0.599976, 0.637512, 0.674988, 0.712524, 0.750000, + 0.787476, 0.825012, 0.862488, 0.900024, 0.937500, + 0.974976, 1.012512, 1.049988, 1.087524, 1.125000, + 1.162476, 1.200012} + + The gains of the subsequent two stages can be either positive or + negative. The gains are quantized by using a quantization table + times a scale factor. The second stage uses the table gain_sq4Tbl, + and the third stage uses gain_sq3Tbl. The scale factor equates 0.1 + + + +Andersen, et al. Experimental [Page 27] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + or the absolute value of the quantized gain representation value + obtained in the previous stage, whichever is larger. Again, the + resulting gain index is the index to the nearest value of the + quantization table times the scale factor. + + gainQ = scaleFact * gain_sqXTbl[index] + + gain_sq4Tbl[16]={-1.049988, -0.900024, -0.750000, -0.599976, + -0.450012, -0.299988, -0.150024, 0.000000, 0.150024, + 0.299988, 0.450012, 0.599976, 0.750000, 0.900024, + 1.049988, 1.200012} + + gain_sq3Tbl[8]={-1.000000, -0.659973, -0.330017,0.000000, + 0.250000, 0.500000, 0.750000, 1.00000} + +3.6.4.3. Preparation of Target for Next Stage + + Before performing the search for the next stage, the perceptually + weighted target vector is updated by subtracting from it the selected + codebook vector (from the perceptually weighted codebook) times the + corresponding quantized gain. + + target[i] = target[i] - gainQ * selected_vec[i]; + + A reference implementation of the codebook encoding is found in + Appendix A.34. + +3.7. Gain Correction Encoding + + The start state is quantized in a relatively model independent manner + using 3 bits per sample. In contrast, the remaining parts of the + block are encoded by using an adaptive codebook. This codebook will + produce high matching accuracy whenever there is a high correlation + between the target and the best codebook vector. For unvoiced speech + segments and background noises, this is not necessarily so, which, + due to the nature of the squared error criterion, results in a coded + signal with less power than the target signal. As the coded start + state has good power matching to the target, the result is a power + fluctuation within the encoded frame. Perceptually, the main problem + with this is that the time envelope of the signal energy becomes + unsteady. To overcome this problem, the gains for the codebooks are + re-scaled after the codebook encoding by searching for a new gain + factor for the first stage codebook that provides better power + matching. + + First, the energy for the target signal, tene, is computed along with + the energy for the coded signal, cene, given by the addition of the + three gain scaled codebook vectors. Because the gains of the second + + + +Andersen, et al. Experimental [Page 28] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + and third stage scale with the gain of the first stage, when the + first stage gain is changed from gain[0] to gain_sq5Tbl[i] the energy + of the coded signal changes from cene to + + cene*(gain_sq5Tbl[i]*gain_sq5Tbl[i])/(gain[0]*gain[0]) + + where gain[0] is the gain for the first stage found in the original + codebook search. A refined search is performed by testing the gain + indices i=0 to 31, and as long as the new codebook energy as given + above is less than tene, the gain index for stage 1 is increased. A + restriction is applied so that the new gain value for stage 1 cannot + be more than two times higher than the original value found in the + codebook search. Note that by using this method we do not change the + shape of the encoded vector, only the gain or amplitude. + +3.8. Bitstream Definition + + The total number of bits used to describe one frame of 20 ms speech + is 304, which fits in 38 bytes and results in a bit rate of 15.20 + kbit/s. For the case of a frame length of 30 ms speech, the total + number of bits used is 400, which fits in 50 bytes and results in a + bit rate of 13.33 kbit/s. In the bitstream definition, the bits are + distributed into three classes according to their bit error or loss + sensitivity. The most sensitive bits (class 1) are placed first in + the bitstream for each frame. The less sensitive bits (class 2) are + placed after the class 1 bits. The least sensitive bits (class 3) + are placed at the end of the bitstream for each frame. + + In the 20/30 ms frame length cases for each class, the following hold + true: The class 1 bits occupy a total of 6/8 bytes (48/64 bits), the + class 2 bits occupy 8/12 bytes (64/96 bits), and the class 3 bits + occupy 24/30 bytes (191/239 bits). This distribution of the bits + enables the use of uneven level protection (ULP) as is exploited in + the payload format definition for iLBC [1]. The detailed bit + allocation is shown in the table below. When a quantization index is + distributed between more classes, the more significant bits belong to + the lowest class. + + + + + + + + + + + + + + +Andersen, et al. Experimental [Page 29] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + Bitstream structure: + + ------------------------------------------------------------------+ + Parameter | Bits Class <1,2,3> | + | 20 ms frame | 30 ms frame | + ----------------------------------+---------------+---------------+ + Split 1 | 6 <6,0,0> | 6 <6,0,0> | + LSF 1 Split 2 | 7 <7,0,0> | 7 <7,0,0> | + LSF Split 3 | 7 <7,0,0> | 7 <7,0,0> | + ------------------+---------------+---------------+ + Split 1 | NA (Not Appl.)| 6 <6,0,0> | + LSF 2 Split 2 | NA | 7 <7,0,0> | + Split 3 | NA | 7 <7,0,0> | + ------------------+---------------+---------------+ + Sum | 20 <20,0,0> | 40 <40,0,0> | + ----------------------------------+---------------+---------------+ + Block Class | 2 <2,0,0> | 3 <3,0,0> | + ----------------------------------+---------------+---------------+ + Position 22 sample segment | 1 <1,0,0> | 1 <1,0,0> | + ----------------------------------+---------------+---------------+ + Scale Factor State Coder | 6 <6,0,0> | 6 <6,0,0> | + ----------------------------------+---------------+---------------+ + Sample 0 | 3 <0,1,2> | 3 <0,1,2> | + Quantized Sample 1 | 3 <0,1,2> | 3 <0,1,2> | + Residual : | : : | : : | + State : | : : | : : | + Samples : | : : | : : | + Sample 56 | 3 <0,1,2> | 3 <0,1,2> | + Sample 57 | NA | 3 <0,1,2> | + ------------------+---------------+---------------+ + Sum | 171 <0,57,114>| 174 <0,58,116>| + ----------------------------------+---------------+---------------+ + Stage 1 | 7 <6,0,1> | 7 <4,2,1> | + CB for 22/23 Stage 2 | 7 <0,0,7> | 7 <0,0,7> | + sample block Stage 3 | 7 <0,0,7> | 7 <0,0,7> | + ------------------+---------------+---------------+ + Sum | 21 <6,0,15> | 21 <4,2,15> | + ----------------------------------+---------------+---------------+ + Stage 1 | 5 <2,0,3> | 5 <1,1,3> | + Gain for 22/23 Stage 2 | 4 <1,1,2> | 4 <1,1,2> | + sample block Stage 3 | 3 <0,0,3> | 3 <0,0,3> | + ------------------+---------------+---------------+ + Sum | 12 <3,1,8> | 12 <2,2,8> | + ----------------------------------+---------------+---------------+ + Stage 1 | 8 <7,0,1> | 8 <6,1,1> | + sub-block 1 Stage 2 | 7 <0,0,7> | 7 <0,0,7> | + Stage 3 | 7 <0,0,7> | 7 <0,0,7> | + ------------------+---------------+---------------+ + + + +Andersen, et al. Experimental [Page 30] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + Stage 1 | 8 <0,0,8> | 8 <0,7,1> | + sub-block 2 Stage 2 | 8 <0,0,8> | 8 <0,0,8> | + Indices Stage 3 | 8 <0,0,8> | 8 <0,0,8> | + for CB ------------------+---------------+---------------+ + sub-blocks Stage 1 | NA | 8 <0,7,1> | + sub-block 3 Stage 2 | NA | 8 <0,0,8> | + Stage 3 | NA | 8 <0,0,8> | + ------------------+---------------+---------------+ + Stage 1 | NA | 8 <0,7,1> | + sub-block 4 Stage 2 | NA | 8 <0,0,8> | + Stage 3 | NA | 8 <0,0,8> | + ------------------+---------------+---------------+ + Sum | 46 <7,0,39> | 94 <6,22,66> | + ----------------------------------+---------------+---------------+ + Stage 1 | 5 <1,2,2> | 5 <1,2,2> | + sub-block 1 Stage 2 | 4 <1,1,2> | 4 <1,2,1> | + Stage 3 | 3 <0,0,3> | 3 <0,0,3> | + ------------------+---------------+---------------+ + Stage 1 | 5 <1,1,3> | 5 <0,2,3> | + sub-block 2 Stage 2 | 4 <0,2,2> | 4 <0,2,2> | + Stage 3 | 3 <0,0,3> | 3 <0,0,3> | + Gains for ------------------+---------------+---------------+ + sub-blocks Stage 1 | NA | 5 <0,1,4> | + sub-block 3 Stage 2 | NA | 4 <0,1,3> | + Stage 3 | NA | 3 <0,0,3> | + ------------------+---------------+---------------+ + Stage 1 | NA | 5 <0,1,4> | + sub-block 4 Stage 2 | NA | 4 <0,1,3> | + Stage 3 | NA | 3 <0,0,3> | + ------------------+---------------+---------------+ + Sum | 24 <3,6,15> | 48 <2,12,34> | + ----------------------------------+---------------+---------------+ + Empty frame indicator | 1 <0,0,1> | 1 <0,0,1> | + ------------------------------------------------------------------- + SUM 304 <48,64,192> 400 <64,96,240> + + Table 3.2. The bitstream definition for iLBC for both the 20 ms + frame size mode and the 30 ms frame size mode. + + When packetized into the payload, the bits MUST be sorted as follows: + All the class 1 bits in the order (from top to bottom) as specified + in the table, all the class 2 bits (from top to bottom), and all the + class 3 bits in the same sequential order. The last bit, the empty + frame indicator, SHOULD be set to zero by the encoder. If this bit + is set to 1 the decoder SHOULD treat the data as a lost frame. For + example, this bit can be set to 1 to indicate lost frame for file + storage format, as in [1]. + + + + +Andersen, et al. Experimental [Page 31] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + +4. Decoder Principles + + This section describes the principles of each component of the + decoder algorithm. + + +-------------+ +--------+ +---------------+ + payload -> | 1. Get para | -> | 2. LPC | -> | 3. Sc Dequant | -> + +-------------+ +--------+ +---------------+ + + +-------------+ +------------------+ + -> | 4. Mem setup| -> | 5. Construct res |-------> + | +-------------+ +------------------- | + ---------<-----------<-----------<------------ + Sub-frame 0...2/4 (20 ms/30 ms) + + +----------------+ +----------+ + -> | 6. Enhance res | -> | 7. Synth | ------------> + +----------------+ +----------+ + + +-----------------+ + -> | 8. Post Process | ----------------> decoded speech + +-----------------+ + + Figure 4.1. Flow chart of the iLBC decoder. If a frame was lost, + steps 1 to 5 SHOULD be replaced by a PLC algorithm. + + 1. Extract the parameters from the bitstream. + + 2. Decode the LPC and interpolate (section 4.1). + + 3. Construct the 57/58-sample start state (section 4.2). + + 4. Set up the memory by using data from the decoded residual. This + memory is used for codebook construction. For blocks preceding + the start state, both the decoded residual and the target are time + reversed. Sub-frames are decoded in the same order as they were + encoded. + + 5. Construct the residuals of this sub-frame (gain[0]*cbvec[0] + + gain[1]*cbvec[1] + gain[2]*cbvec[2]). Repeat 4 and 5 until the + residual of all sub-blocks has been constructed. + + 6. Enhance the residual with the post filter (section 4.6). + + 7. Synthesis of the residual (section 4.7). + + 8. Post process with HP filter, if desired (section 4.8). + + + + +Andersen, et al. Experimental [Page 32] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + +4.1. LPC Filter Reconstruction + + The decoding of the LP filter parameters is very straightforward. + For a set of three/six indices, the corresponding LSF vector(s) are + found by simple table lookup. For each of the LSF vectors, the three + split vectors are concatenated to obtain qlsf1 and qlsf2, + respectively (in the 20 ms mode only one LSF vector, qlsf, is + constructed). The next step is the stability check described in + section 3.2.5 followed by the interpolation scheme described in + section 3.2.6 (3.2.7 for 20 ms frames). The only difference is that + only the quantized LSFs are known at the decoder, and hence the + unquantized LSFs are not processed. + + A reference implementation of the LPC filter reconstruction is given + in Appendix A.36. + +4.2. Start State Reconstruction + + The scalar encoded STATE_SHORT_LEN=58 (STATE_SHORT_LEN=57 in the 20 + ms mode) state samples are reconstructed by 1) forming a set of + samples (by table lookup) from the index stream idxVec[n], 2) + multiplying the set with 1/scal=(10^qmax)/4.5, 3) time reversing the + 57/58 samples, 4) filtering the time reversed block with the + dispersion (all-pass) filter used in the encoder (as described in + section 3.5.2); this compensates for the phase distortion of the + earlier filter operation, and 5 reversing the 57/58 samples from the + previous step. + + in(0..(STATE_SHORT_LEN-1)) = time reversed samples from table + look-up, + idxVecDec((STATE_SHORT_LEN-1)..0) + + in(STATE_SHORT_LEN..(2*STATE_SHORT_LEN-1)) = 0 + + Pk(z) = A~rk(z)/A~k(z), where + ___ + \ + A~rk(z)= z^(-LPC_FILTERORDER) + > a~ki*z^(i-(LPC_FILTERORDER-1)) + /__ + i=0...(LPC_FILTERORDER-1) + + and A~k(z) is taken from the block where the start state begins + + in -> Pk(z) -> filtered + + out(k) = filtered(STATE_SHORT_LEN-1-k) + + filtered(2*STATE_SHORT_LEN-1-k), + k=0..(STATE_SHORT_LEN-1) + + + +Andersen, et al. Experimental [Page 33] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + The remaining 23/22 samples in the state are reconstructed by the + same adaptive codebook technique described in section 4.3. The + location bit determines whether these are the first or the last 23/22 + samples of the 80-sample state vector. If the remaining 23/22 + samples are the first samples, then the scalar encoded + STATE_SHORT_LEN state samples are time-reversed before initialization + of the adaptive codebook memory vector. + + A reference implementation of the start state reconstruction is given + in Appendix A.44. + +4.3. Excitation Decoding Loop + + The decoding of the LPC excitation vector proceeds in the same order + in which the residual was encoded at the encoder. That is, after the + decoding of the entire 80-sample state vector, the forward sub-blocks + (corresponding to samples occurring after the state vector samples) + are decoded, and then the backward sub-blocks (corresponding to + samples occurring before the state vector) are decoded, resulting in + a fully decoded block of excitation signal samples. + + In particular, each sub-block is decoded by using the multistage + adaptive codebook decoding module described in section 4.4. This + module relies upon an adaptive codebook memory constructed before + each run of the adaptive codebook decoding. The construction of the + adaptive codebook memory in the decoder is identical to the method + outlined in section 3.6.3, except that it is done on the codebook + memory without perceptual weighting. + + For the initial forward sub-block, the last STATE_LEN=80 samples of + the length CB_LMEM=147 adaptive codebook memory are filled with the + samples of the state vector. For subsequent forward sub-blocks, the + first SUBL=40 samples of the adaptive codebook memory are discarded, + the remaining samples are shifted by SUBL samples toward the + beginning of the vector, and the newly decoded SUBL=40 samples are + placed at the end of the adaptive codebook memory. For backward + sub-blocks, the construction is similar, except that every vector of + samples involved is first time reversed. + + A reference implementation of the excitation decoding loop is found + in Appendix A.5. + + + + + + + + + + +Andersen, et al. Experimental [Page 34] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + +4.4. Multistage Adaptive Codebook Decoding + + The Multistage Adaptive Codebook Decoding module is used at both the + sender (encoder) and the receiver (decoder) ends to produce a + synthetic signal in the residual domain that is eventually used to + produce synthetic speech. The module takes the index values used to + construct vectors that are scaled and summed together to produce a + synthetic signal that is the output of the module. + +4.4.1. Construction of the Decoded Excitation Signal + + The unpacked index values provided at the input to the module are + references to extended codebooks, which are constructed as described + in section 3.6.3, except that they are based on the codebook memory + without the perceptual weighting. The unpacked three indices are + used to look up three codebook vectors. The unpacked three gain + indices are used to decode the corresponding 3 gains. In this + decoding, the successive rescaling, as described in section 3.6.4.2, + is applied. + + A reference implementation of the adaptive codebook decoding is + listed in Appendix A.32. + +4.5. Packet Loss Concealment + + If packet loss occurs, the decoder receives a signal saying that + information regarding a block is lost. For such blocks it is + RECOMMENDED to use a Packet Loss Concealment (PLC) unit to create a + decoded signal that masks the effect of that packet loss. In the + following we will describe an example of a PLC unit that can be used + with the iLBC codec. As the PLC unit is used only at the decoder, + the PLC unit does not affect interoperability between + implementations. Other PLC implementations MAY therefore be used. + + The PLC described operates on the LP filters and the excitation + signals and is based on the following principles: + +4.5.1. Block Received Correctly and Previous Block Also Received + + If the block is received correctly, the PLC only records state + information of the current block that can be used in case the next + block is lost. The LP filter coefficients for each sub-block and the + entire decoded excitation signal are all saved in the decoder state + structure. All of this information will be needed if the following + block is lost. + + + + + + +Andersen, et al. Experimental [Page 35] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + +4.5.2. Block Not Received + + If the block is not received, the block substitution is based on a + pitch-synchronous repetition of the excitation signal, which is + filtered by the last LP filter of the previous block. The previous + block's information is stored in the decoder state structure. + + A correlation analysis is performed on the previous block's + excitation signal in order to detect the amount of pitch periodicity + and a pitch value. The correlation measure is also used to decide on + the voicing level (the degree to which the previous block's + excitation was a voiced or roughly periodic signal). The excitation + in the previous block is used to create an excitation for the block + to be substituted, such that the pitch of the previous block is + maintained. Therefore, the new excitation is constructed in a + pitch-synchronous manner. In order to avoid a buzzy-sounding + substituted block, a random excitation is mixed with the new pitch + periodic excitation, and the relative use of the two components is + computed from the correlation measure (voicing level). + + For the block to be substituted, the newly constructed excitation + signal is then passed through the LP filter to produce the speech + that will be substituted for the lost block. + + For several consecutive lost blocks, the packet loss concealment + continues in a similar manner. The correlation measure of the last + block received is still used along with the same pitch value. The LP + filters of the last block received are also used again. The energy + of the substituted excitation for consecutive lost blocks is + decreased, leading to a dampened excitation, and therefore to + dampened speech. + +4.5.3. Block Received Correctly When Previous Block Not Received + + For the case in which a block is received correctly when the previous + block was not, the correctly received block's directly decoded speech + (based solely on the received block) is not used as the actual + output. The reason for this is that the directly decoded speech does + not necessarily smoothly merge into the synthetic speech generated + for the previous lost block. If the two signals are not smoothly + merged, an audible discontinuity is accidentally produced. + Therefore, a correlation analysis between the two blocks of + excitation signal (the excitation of the previous concealed block and + that of the current received block) is performed to find the best + phase match. Then a simple overlap-add procedure is performed to + merge the previous excitation smoothly into the current block's + excitation. + + + + +Andersen, et al. Experimental [Page 36] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + The exact implementation of the packet loss concealment does not + influence interoperability of the codec. + + A reference implementation of the packet loss concealment is + suggested in Appendix A.14. Exact compliance with this suggested + algorithm is not needed for a reference implementation to be fully + compatible with the overall codec specification. + +4.6. Enhancement + + The decoder contains an enhancement unit that operates on the + reconstructed excitation signal. The enhancement unit increases the + perceptual quality of the reconstructed signal by reducing the + speech-correlated noise in the voiced speech segments. Compared to + traditional postfilters, the enhancer has an advantage in that it can + only modify the excitation signal slightly. This means that there is + no risk of over enhancement. The enhancer works very similarly for + both the 20 ms frame size mode and the 30 ms frame size mode. + + For the mode with 20 ms frame size, the enhancer uses a memory of six + 80-sample excitation blocks prior in time plus the two new 80-sample + excitation blocks. For each block of 160 new unenhanced excitation + samples, 160 enhanced excitation samples are produced. The enhanced + excitation is 40-sample delayed compared to the unenhanced + excitation, as the enhancer algorithm uses lookahead. + + For the mode with 30 ms frame size, the enhancer uses a memory of + five 80-sample excitation blocks prior in time plus the three new + 80-sample excitation blocks. For each block of 240 new unenhanced + excitation samples, 240 enhanced excitation samples are produced. + The enhanced excitation is 80-sample delayed compared to the + unenhanced excitation, as the enhancer algorithm uses lookahead. + + Outline of Enhancer + + The speech enhancement unit operates on sub-blocks of 80 samples, + which means that there are two/three 80 sample sub-blocks per frame. + Each of these two/three sub-blocks is enhanced separately, but in an + analogous manner. + + + + + + + + + + + + +Andersen, et al. Experimental [Page 37] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + unenhanced residual + | + | +---------------+ +--------------+ + +-> | 1. Pitch Est | -> | 2. Find PSSQ | --------> + +---------------+ | +--------------+ + +-----<-------<------<--+ + +------------+ enh block 0..1/2 | + -> | 3. Smooth | | + +------------+ | + \ | + /\ | + / \ Already | + / 4. \----------->----------->-----------+ | + \Crit/ Fulfilled | | + \? / v | + \/ | | + \ +-----------------+ +---------+ | | + Not +->| 5. Use Constr. | -> | 6. Mix | -----> + Fulfilled +-----------------+ +---------+ + + ---------------> enhanced residual + + Figure 4.2. Flow chart of the enhancer. + + 1. Pitch estimation of each of the two/three new 80-sample blocks. + + 2. Find the pitch-period-synchronous sequence n (for block k) by a + search around the estimated pitch value. Do this for n=1,2,3, + -1,-2,-3. + + 3. Calculate the smoothed residual generated by the six pitch- + period-synchronous sequences from prior step. + + 4. Check if the smoothed residual satisfies the criterion (section + 4.6.4). + + 5. Use constraint to calculate mixing factor (section 4.6.5). + + 6. Mix smoothed signal with unenhanced residual (pssq(n) n=0). + + The main idea of the enhancer is to find three 80 sample blocks + before and three 80-sample blocks after the analyzed unenhanced sub- + block and to use these to improve the quality of the excitation in + that sub-block. The six blocks are chosen so that they have the + highest possible correlation with the unenhanced sub-block that is + being enhanced. In other words, the six blocks are pitch-period- + synchronous sequences to the unenhanced sub-block. + + + + +Andersen, et al. Experimental [Page 38] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + A linear combination of the six pitch-period-synchronous sequences is + calculated that approximates the sub-block. If the squared error + between the approximation and the unenhanced sub-block is small + enough, the enhanced residual is set equal to this approximation. + For the cases when the squared error criterion is not fulfilled, a + linear combination of the approximation and the unenhanced residual + forms the enhanced residual. + +4.6.1. Estimating the Pitch + + Pitch estimates are needed to determine the locations of the pitch- + period-synchronous sequences in a complexity-efficient way. For each + of the new two/three sub-blocks, a pitch estimate is calculated by + finding the maximum correlation in the range from lag 20 to lag 120. + These pitch estimates are used to narrow down the search for the best + possible pitch-period-synchronous sequences. + +4.6.2. Determination of the Pitch-Synchronous Sequences + + Upon receiving the pitch estimates from the prior step, the enhancer + analyzes and enhances one 80-sample sub-block at a time. The pitch- + period-synchronous-sequences pssq(n) can be viewed as vectors of + length 80 samples each shifted n*lag samples from the current sub- + block. The six pitch-period-synchronous-sequences, pssq(-3) to + pssq(-1) and pssq(1) to pssq(3), are found one at a time by the steps + below: + + 1) Calculate the estimate of the position of the pssq(n). For + pssq(n) in front of pssq(0) (n > 0), the location of the pssq(n) + is estimated by moving one pitch estimate forward in time from the + exact location of pssq(n-1). Similarly, pssq(n) behind pssq(0) (n + < 0) is estimated by moving one pitch estimate backward in time + from the exact location of pssq(n+1). If the estimated pssq(n) + vector location is totally within the enhancer memory (Figure + 4.3), steps 2, 3, and 4 are performed, otherwise the pssq(n) is + set to zeros. + + 2) Compute the correlation between the unenhanced excitation and + vectors around the estimated location interval of pssq(n). The + correlation is calculated in the interval estimated location +/- 2 + samples. This results in five correlation values. + + 3) The five correlation values are upsampled by a factor of 4, by + using four simple upsampling filters (MA filters with coefficients + upsFilter1.. upsFilter4). Within these the maximum value is + found, which specifies the best pitch-period with a resolution of + a quarter of a sample. + + + + +Andersen, et al. Experimental [Page 39] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + upsFilter1[7]={0.000000 0.000000 0.000000 1.000000 + 0.000000 0.000000 0.000000} + upsFilter2[7]={0.015625 -0.076904 0.288330 0.862061 + -0.106445 0.018799 -0.015625} + upsFilter3[7]={0.023682 -0.124268 0.601563 0.601563 + -0.124268 0.023682 -0.023682} + upsFilter4[7]={0.018799 -0.106445 0.862061 0.288330 + -0.076904 0.015625 -0.018799} + + 4) Generate the pssq(n) vector by upsampling of the excitation memory + and extracting the sequence that corresponds to the lag delay that + was calculated in prior step. + + With the steps above, all the pssq(n) can be found in an iterative + manner, first moving backward in time from pssq(0) and then forward + in time from pssq(0). + + + 0 159 319 479 639 + +---------------------------------------------------------------+ + | -5 | -4 | -3 | -2 | -1 | 0 | 1 | 2 | + +---------------------------------------------------------------+ + |pssq 0 | + |pssq -1| |pssq 1 | + |pssq -2| |pssq 2 | + |pssq -3| |pssq 3 | + + Figure 4.3. Enhancement for 20 ms frame size. + + Figure 4.3 depicts pitch-period-synchronous sequences in the + enhancement of the first 80 sample block in the 20 ms frame size + mode. The unenhanced signal input is stored in the last two sub- + blocks (1 - 2), and the six other sub-blocks contain unenhanced + residual prior-in-time. We perform the enhancement algorithm on two + blocks of 80 samples, where the first of the two blocks consists of + the last 40 samples of sub-block 0 and the first 40 samples of sub- + block 1. The second 80-sample block consists of the last 40 samples + of sub-block 1 and the first 40 samples of sub-block 2. + + + + + + + + + + + + + +Andersen, et al. Experimental [Page 40] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + 0 159 319 479 639 + +---------------------------------------------------------------+ + | -4 | -3 | -2 | -1 | 0 | 1 | 2 | 3 | + +---------------------------------------------------------------+ + |pssq 0 | + |pssq -1| |pssq 1 | + |pssq -2| |pssq 2 | + |pssq -3| |pssq 3 | + + Figure 4.4. Enhancement for 30 ms frame size. + + Figure 4.4 depicts pitch-period-synchronous sequences in the + enhancement of the first 80-sample block in the 30 ms frame size + mode. The unenhanced signal input is stored in the last three sub- + blocks (1 - 3). The five other sub-blocks contain unenhanced + residual prior-in-time. The enhancement algorithm is performed on + the three 80 sample sub-blocks 0, 1, and 2. + +4.6.3. Calculation of the Smoothed Excitation + + A linear combination of the six pssq(n) (n!=0) form a smoothed + approximation, z, of pssq(0). Most of the weight is put on the + sequences that are close to pssq(0), as these are likely to be most + similar to pssq(0). The smoothed vector is also rescaled so that the + energy of z is the same as the energy of pssq(0). + + ___ + \ + y = > pssq(i) * pssq_weight(i) + /__ + i=-3,-2,-1,1,2,3 + + pssq_weight(i) = 0.5*(1-cos(2*pi*(i+4)/(2*3+2))) + + z = C * y, where C = ||pssq(0)||/||y|| + +4.6.4. Enhancer Criterion + + The criterion of the enhancer is that the enhanced excitation is not + allowed to differ much from the unenhanced excitation. This + criterion is checked for each 80-sample sub-block. + + e < (b * ||pssq(0)||^2), where b=0.05 and (Constraint 1) + + e = (pssq(0)-z)*(pssq(0)-z), and "*" means the dot product + + + + + + +Andersen, et al. Experimental [Page 41] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + +4.6.5. Enhancing the excitation + + From the criterion in the previous section, it is clear that the + excitation is not allowed to change much. The purpose of this + constraint is to prevent the creation of an enhanced signal + significantly different from the original signal. This also means + that the constraint limits the numerical size of the errors that the + enhancement procedure can make. That is especially important in + unvoiced segments and background noise segments for which increased + periodicity could lead to lower perceived quality. + + When the constraint in the prior section is not met, the enhanced + residual is instead calculated through a constrained optimization by + using the Lagrange multiplier technique. The new constraint is that + + e = (b * ||pssq(0)||^2) (Constraint 2) + + We distinguish two solution regions for the optimization: 1) the + region where the first constraint is fulfilled and 2) the region + where the first constraint is not fulfilled and the second constraint + must be used. + + In the first case, where the second constraint is not needed, the + optimized re-estimated vector is simply z, the energy-scaled version + of y. + + In the second case, where the second constraint is activated and + becomes an equality constraint, we have + + z= A*y + B*pssq(0) + + where + + A = sqrt((b-b^2/4)*(w00*w00)/ (w11*w00 + w10*w10)) and + + w11 = pssq(0)*pssq(0) + w00 = y*y + w10 = y*pssq(0) (* symbolizes the dot product) + + and + + B = 1 - b/2 - A * w10/w00 + + Appendix A.16 contains a listing of a reference implementation for + the enhancement method. + + + + + + +Andersen, et al. Experimental [Page 42] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + +4.7. Synthesis Filtering + + Upon decoding or PLC of the LP excitation block, the decoded speech + block is obtained by running the decoded LP synthesis filter, + 1/A~k(z), over the block. The synthesis filters have to be shifted + to compensate for the delay in the enhancer. For 20 ms frame size + mode, they SHOULD be shifted one 40-sample sub-block, and for 30 ms + frame size mode, they SHOULD be shifted two 40-sample sub-blocks. + The LP coefficients SHOULD be changed at the first sample of every + sub-block while keeping the filter state. For PLC blocks, one + solution is to apply the last LP coefficients of the last decoded + speech block for all sub-blocks. + + The reference implementation for the synthesis filtering can be found + in Appendix A.48. + +4.8. Post Filtering + + If desired, the decoded block can be filtered by a high-pass filter. + This removes the low frequencies of the decoded signal. A reference + implementation of this, with cutoff at 65 Hz, is shown in Appendix + A.30. + +5. Security Considerations + + This algorithm for the coding of speech signals is not subject to any + known security consideration; however, its RTP payload format [1] is + subject to several considerations, which are addressed there. + Confidentiality of the media streams is achieved by encryption; + therefore external mechanisms, such as SRTP [5], MAY be used for that + purpose. + +6. Evaluation of the iLBC Implementations + + It is possible and suggested to evaluate certain iLBC implementation + by utilizing methodology and tools available at + http://www.ilbcfreeware.org/evaluation.html + +7. References + +7.1. Normative References + + [1] Duric, A. and S. Andersen, "Real-time Transport Protocol (RTP) + Payload Format for internet Low Bit Rate Codec (iLBC) Speech", + RFC 3952, December 2004. + + [2] Bradner, S., "Key words for use in RFCs to Indicate Requirement + Levels", BCP 14, RFC 2119, March 1997. + + + +Andersen, et al. Experimental [Page 43] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + [3] PacketCable(TM) Audio/Video Codecs Specification, Cable + Television Laboratories, Inc. + +7.2. Informative References + + [4] ITU-T Recommendation G.711, available online from the ITU + bookstore at http://www.itu.int. + + [5] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K. Norman, + "The Secure Real Time Transport Protocol (SRTP)", RFC 3711, March + 2004. + +8. Acknowledgements + + This extensive work, besides listed authors, has the following + authors, who could not have been listed among "official" authors (due + to IESG restrictions in the number of authors who can be listed): + + Manohar N. Murthi (Department of Electrical and Computer + Engineering, University of Miami), Fredrik Galschiodt, Julian + Spittka, and Jan Skoglund (Global IP Sound). + + The authors are deeply indebted to the following people and thank + them sincerely: + + Henry Sinnreich, Patrik Faltstrom, Alan Johnston, and Jean- + Francois Mule for great support of the iLBC initiative and for + valuable feedback and comments. + + Peter Vary, Frank Mertz, and Christoph Erdmann (RWTH Aachen); + Vladimir Cuperman (Niftybox LLC); Thomas Eriksson (Chalmers Univ + of Tech), and Gernot Kubin (TU Graz), for thorough review of the + iLBC document and their valuable feedback and remarks. + + + + + + + + + + + + + + + + + + +Andersen, et al. Experimental [Page 44] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + +APPENDIX A. Reference Implementation + + This appendix contains the complete c-code for a reference + implementation of encoder and decoder for the specified codec. + + The c-code consists of the following files with highest-level + functions: + + iLBC_test.c: main function for evaluation purpose + iLBC_encode.h: encoder header + iLBC_encode.c: encoder function + iLBC_decode.h: decoder header + iLBC_decode.c: decoder function + + The following files contain global defines and constants: + + iLBC_define.h: global defines + constants.h: global constants header + constants.c: global constants memory allocations + + The following files contain subroutines: + + anaFilter.h: lpc analysis filter header + anaFilter.c: lpc analysis filter function + createCB.h: codebook construction header + createCB.c: codebook construction function + doCPLC.h: packet loss concealment header + doCPLC.c: packet loss concealment function + enhancer.h: signal enhancement header + enhancer.c: signal enhancement function + filter.h: general filter header + filter.c: general filter functions + FrameClassify.h: start state classification header + FrameClassify.c: start state classification function + gainquant.h: gain quantization header + gainquant.c: gain quantization function + getCBvec.h: codebook vector construction header + getCBvec.c: codebook vector construction function + helpfun.h: general purpose header + helpfun.c: general purpose functions + hpInput.h: input high pass filter header + hpInput.c: input high pass filter function + hpOutput.h: output high pass filter header + hpOutput.c: output high pass filter function + iCBConstruct.h: excitation decoding header + iCBConstruct.c: excitation decoding function + iCBSearch.h: excitation encoding header + iCBSearch.c: excitation encoding function + + + +Andersen, et al. Experimental [Page 45] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + LPCdecode.h: lpc decoding header + LPCdecode.c: lpc decoding function + LPCencode.h: lpc encoding header + LPCencode.c: lpc encoding function + lsf.h: line spectral frequencies header + lsf.c: line spectral frequencies functions + packing.h: bitstream packetization header + packing.c: bitstream packetization functions + StateConstructW.h: state decoding header + StateConstructW.c: state decoding functions + StateSearchW.h: state encoding header + StateSearchW.c: state encoding function + syntFilter.h: lpc synthesis filter header + syntFilter.c: lpc synthesis filter function + + The implementation is portable and should work on many different + platforms. However, it is not difficult to optimize the + implementation on particular platforms, an exercise left to the + reader. + +A.1. iLBC_test.c + + /****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + iLBC_test.c + + Copyright (C) The Internet Society (2004). + All Rights Reserved. + + ******************************************************************/ + + #include <math.h> + #include <stdlib.h> + #include <stdio.h> + #include <string.h> + #include "iLBC_define.h" + #include "iLBC_encode.h" + #include "iLBC_decode.h" + + /* Runtime statistics */ + #include <time.h> + + #define ILBCNOOFWORDS_MAX (NO_OF_BYTES_30MS/2) + + /*----------------------------------------------------------------* + * Encoder interface function + + + +Andersen, et al. Experimental [Page 46] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + *---------------------------------------------------------------*/ + + short encode( /* (o) Number of bytes encoded */ + iLBC_Enc_Inst_t *iLBCenc_inst, + /* (i/o) Encoder instance */ + short *encoded_data, /* (o) The encoded bytes */ + short *data /* (i) The signal block to encode*/ + ){ + float block[BLOCKL_MAX]; + int k; + + /* convert signal to float */ + + for (k=0; k<iLBCenc_inst->blockl; k++) + block[k] = (float)data[k]; + + /* do the actual encoding */ + + iLBC_encode((unsigned char *)encoded_data, block, iLBCenc_inst); + + + return (iLBCenc_inst->no_of_bytes); + } + + /*----------------------------------------------------------------* + * Decoder interface function + *---------------------------------------------------------------*/ + + short decode( /* (o) Number of decoded samples */ + iLBC_Dec_Inst_t *iLBCdec_inst, /* (i/o) Decoder instance */ + short *decoded_data, /* (o) Decoded signal block*/ + short *encoded_data, /* (i) Encoded bytes */ + short mode /* (i) 0=PL, 1=Normal */ + ){ + int k; + float decblock[BLOCKL_MAX], dtmp; + + /* check if mode is valid */ + + if (mode<0 || mode>1) { + printf("\nERROR - Wrong mode - 0, 1 allowed\n"); exit(3);} + + /* do actual decoding of block */ + + iLBC_decode(decblock, (unsigned char *)encoded_data, + iLBCdec_inst, mode); + + /* convert to short */ + + + +Andersen, et al. Experimental [Page 47] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + for (k=0; k<iLBCdec_inst->blockl; k++){ + dtmp=decblock[k]; + + if (dtmp<MIN_SAMPLE) + dtmp=MIN_SAMPLE; + else if (dtmp>MAX_SAMPLE) + dtmp=MAX_SAMPLE; + decoded_data[k] = (short) dtmp; + } + + return (iLBCdec_inst->blockl); + } + + /*---------------------------------------------------------------* + * Main program to test iLBC encoding and decoding + * + * Usage: + * exefile_name.exe <infile> <bytefile> <outfile> <channel> + * + * <infile> : Input file, speech for encoder (16-bit pcm file) + * <bytefile> : Bit stream output from the encoder + * <outfile> : Output file, decoded speech (16-bit pcm file) + * <channel> : Bit error file, optional (16-bit) + * 1 - Packet received correctly + * 0 - Packet Lost + * + *--------------------------------------------------------------*/ + + int main(int argc, char* argv[]) + { + + /* Runtime statistics */ + + float starttime; + float runtime; + float outtime; + + FILE *ifileid,*efileid,*ofileid, *cfileid; + short data[BLOCKL_MAX]; + short encoded_data[ILBCNOOFWORDS_MAX], decoded_data[BLOCKL_MAX]; + int len; + short pli, mode; + int blockcount = 0; + int packetlosscount = 0; + + /* Create structs */ + iLBC_Enc_Inst_t Enc_Inst; + iLBC_Dec_Inst_t Dec_Inst; + + + +Andersen, et al. Experimental [Page 48] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + /* get arguments and open files */ + + if ((argc!=5) && (argc!=6)) { + fprintf(stderr, + "\n*-----------------------------------------------*\n"); + fprintf(stderr, + " %s <20,30> input encoded decoded (channel)\n\n", + argv[0]); + fprintf(stderr, + " mode : Frame size for the encoding/decoding\n"); + fprintf(stderr, + " 20 - 20 ms\n"); + fprintf(stderr, + " 30 - 30 ms\n"); + fprintf(stderr, + " input : Speech for encoder (16-bit pcm file)\n"); + fprintf(stderr, + " encoded : Encoded bit stream\n"); + fprintf(stderr, + " decoded : Decoded speech (16-bit pcm file)\n"); + fprintf(stderr, + " channel : Packet loss pattern, optional (16-bit)\n"); + fprintf(stderr, + " 1 - Packet received correctly\n"); + fprintf(stderr, + " 0 - Packet Lost\n"); + fprintf(stderr, + "*-----------------------------------------------*\n\n"); + exit(1); + } + mode=atoi(argv[1]); + if (mode != 20 && mode != 30) { + fprintf(stderr,"Wrong mode %s, must be 20, or 30\n", + argv[1]); + exit(2); + } + if ( (ifileid=fopen(argv[2],"rb")) == NULL) { + fprintf(stderr,"Cannot open input file %s\n", argv[2]); + exit(2);} + if ( (efileid=fopen(argv[3],"wb")) == NULL) { + fprintf(stderr, "Cannot open encoded file %s\n", + argv[3]); exit(1);} + if ( (ofileid=fopen(argv[4],"wb")) == NULL) { + fprintf(stderr, "Cannot open decoded file %s\n", + argv[4]); exit(1);} + if (argc==6) { + if( (cfileid=fopen(argv[5],"rb")) == NULL) { + fprintf(stderr, "Cannot open channel file %s\n", + + + +Andersen, et al. Experimental [Page 49] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + argv[5]); + exit(1); + } + } else { + cfileid=NULL; + } + + /* print info */ + + fprintf(stderr, "\n"); + fprintf(stderr, + "*---------------------------------------------------*\n"); + fprintf(stderr, + "* *\n"); + fprintf(stderr, + "* iLBC test program *\n"); + fprintf(stderr, + "* *\n"); + fprintf(stderr, + "* *\n"); + fprintf(stderr, + "*---------------------------------------------------*\n"); + fprintf(stderr,"\nMode : %2d ms\n", mode); + fprintf(stderr,"Input file : %s\n", argv[2]); + fprintf(stderr,"Encoded file : %s\n", argv[3]); + fprintf(stderr,"Output file : %s\n", argv[4]); + if (argc==6) { + fprintf(stderr,"Channel file : %s\n", argv[5]); + } + fprintf(stderr,"\n"); + + /* Initialization */ + + initEncode(&Enc_Inst, mode); + initDecode(&Dec_Inst, mode, 1); + + /* Runtime statistics */ + + starttime=clock()/(float)CLOCKS_PER_SEC; + + /* loop over input blocks */ + + while (fread(data,sizeof(short),Enc_Inst.blockl,ifileid)== + Enc_Inst.blockl) { + + blockcount++; + + /* encoding */ + + + +Andersen, et al. Experimental [Page 50] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + fprintf(stderr, "--- Encoding block %i --- ",blockcount); + len=encode(&Enc_Inst, encoded_data, data); + fprintf(stderr, "\r"); + + /* write byte file */ + + fwrite(encoded_data, sizeof(unsigned char), len, efileid); + + /* get channel data if provided */ + if (argc==6) { + if (fread(&pli, sizeof(short), 1, cfileid)) { + if ((pli!=0)&&(pli!=1)) { + fprintf(stderr, "Error in channel file\n"); + exit(0); + } + if (pli==0) { + /* Packet loss -> remove info from frame */ + memset(encoded_data, 0, + sizeof(short)*ILBCNOOFWORDS_MAX); + packetlosscount++; + } + } else { + fprintf(stderr, "Error. Channel file too short\n"); + exit(0); + } + } else { + pli=1; + } + + /* decoding */ + + fprintf(stderr, "--- Decoding block %i --- ",blockcount); + + len=decode(&Dec_Inst, decoded_data, encoded_data, pli); + fprintf(stderr, "\r"); + + /* write output file */ + + fwrite(decoded_data,sizeof(short),len,ofileid); + } + + /* Runtime statistics */ + + runtime = (float)(clock()/(float)CLOCKS_PER_SEC-starttime); + outtime = (float)((float)blockcount*(float)mode/1000.0); + printf("\n\nLength of speech file: %.1f s\n", outtime); + printf("Packet loss : %.1f%%\n", + 100.0*(float)packetlosscount/(float)blockcount); + + + +Andersen, et al. Experimental [Page 51] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + printf("Time to run iLBC :"); + printf(" %.1f s (%.1f %% of realtime)\n\n", runtime, + (100*runtime/outtime)); + + /* close files */ + + fclose(ifileid); fclose(efileid); fclose(ofileid); + if (argc==6) { + fclose(cfileid); + } + return(0); + } + +A.2. iLBC_encode.h + + /****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + iLBC_encode.h + + Copyright (C) The Internet Society (2004). + All Rights Reserved. + + ******************************************************************/ + + #ifndef __iLBC_ILBCENCODE_H + #define __iLBC_ILBCENCODE_H + + #include "iLBC_define.h" + + short initEncode( /* (o) Number of bytes + encoded */ + iLBC_Enc_Inst_t *iLBCenc_inst, /* (i/o) Encoder instance */ + int mode /* (i) frame size mode */ + ); + + void iLBC_encode( + + unsigned char *bytes, /* (o) encoded data bits iLBC */ + float *block, /* (o) speech vector to + encode */ + iLBC_Enc_Inst_t *iLBCenc_inst /* (i/o) the general encoder + state */ + ); + + #endif + + + + +Andersen, et al. Experimental [Page 52] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + +A.3. iLBC_encode.c + + /****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + iLBC_encode.c + + Copyright (C) The Internet Society (2004). + All Rights Reserved. + + ******************************************************************/ + + #include <math.h> + #include <stdlib.h> + #include <string.h> + + #include "iLBC_define.h" + #include "LPCencode.h" + #include "FrameClassify.h" + #include "StateSearchW.h" + #include "StateConstructW.h" + #include "helpfun.h" + #include "constants.h" + #include "packing.h" + #include "iCBSearch.h" + #include "iCBConstruct.h" + #include "hpInput.h" + #include "anaFilter.h" + #include "syntFilter.h" + + /*----------------------------------------------------------------* + * Initiation of encoder instance. + *---------------------------------------------------------------*/ + + short initEncode( /* (o) Number of bytes + encoded */ + iLBC_Enc_Inst_t *iLBCenc_inst, /* (i/o) Encoder instance */ + int mode /* (i) frame size mode */ + ){ + iLBCenc_inst->mode = mode; + if (mode==30) { + iLBCenc_inst->blockl = BLOCKL_30MS; + iLBCenc_inst->nsub = NSUB_30MS; + iLBCenc_inst->nasub = NASUB_30MS; + iLBCenc_inst->lpc_n = LPC_N_30MS; + iLBCenc_inst->no_of_bytes = NO_OF_BYTES_30MS; + iLBCenc_inst->no_of_words = NO_OF_WORDS_30MS; + + + +Andersen, et al. Experimental [Page 53] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + iLBCenc_inst->state_short_len=STATE_SHORT_LEN_30MS; + /* ULP init */ + iLBCenc_inst->ULP_inst=&ULP_30msTbl; + } + else if (mode==20) { + iLBCenc_inst->blockl = BLOCKL_20MS; + iLBCenc_inst->nsub = NSUB_20MS; + iLBCenc_inst->nasub = NASUB_20MS; + iLBCenc_inst->lpc_n = LPC_N_20MS; + iLBCenc_inst->no_of_bytes = NO_OF_BYTES_20MS; + iLBCenc_inst->no_of_words = NO_OF_WORDS_20MS; + iLBCenc_inst->state_short_len=STATE_SHORT_LEN_20MS; + /* ULP init */ + iLBCenc_inst->ULP_inst=&ULP_20msTbl; + } + else { + exit(2); + } + + memset((*iLBCenc_inst).anaMem, 0, + LPC_FILTERORDER*sizeof(float)); + memcpy((*iLBCenc_inst).lsfold, lsfmeanTbl, + LPC_FILTERORDER*sizeof(float)); + memcpy((*iLBCenc_inst).lsfdeqold, lsfmeanTbl, + LPC_FILTERORDER*sizeof(float)); + memset((*iLBCenc_inst).lpc_buffer, 0, + (LPC_LOOKBACK+BLOCKL_MAX)*sizeof(float)); + memset((*iLBCenc_inst).hpimem, 0, 4*sizeof(float)); + + return (iLBCenc_inst->no_of_bytes); + } + + /*----------------------------------------------------------------* + * main encoder function + *---------------------------------------------------------------*/ + + void iLBC_encode( + unsigned char *bytes, /* (o) encoded data bits iLBC */ + float *block, /* (o) speech vector to + encode */ + iLBC_Enc_Inst_t *iLBCenc_inst /* (i/o) the general encoder + state */ + ){ + + float data[BLOCKL_MAX]; + float residual[BLOCKL_MAX], reverseResidual[BLOCKL_MAX]; + + int start, idxForMax, idxVec[STATE_LEN]; + + + +Andersen, et al. Experimental [Page 54] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + float reverseDecresidual[BLOCKL_MAX], mem[CB_MEML]; + int n, k, meml_gotten, Nfor, Nback, i, pos; + int gain_index[CB_NSTAGES*NASUB_MAX], + extra_gain_index[CB_NSTAGES]; + int cb_index[CB_NSTAGES*NASUB_MAX],extra_cb_index[CB_NSTAGES]; + int lsf_i[LSF_NSPLIT*LPC_N_MAX]; + unsigned char *pbytes; + int diff, start_pos, state_first; + float en1, en2; + int index, ulp, firstpart; + int subcount, subframe; + float weightState[LPC_FILTERORDER]; + float syntdenum[NSUB_MAX*(LPC_FILTERORDER+1)]; + float weightdenum[NSUB_MAX*(LPC_FILTERORDER+1)]; + float decresidual[BLOCKL_MAX]; + + /* high pass filtering of input signal if such is not done + prior to calling this function */ + + hpInput(block, iLBCenc_inst->blockl, + data, (*iLBCenc_inst).hpimem); + + /* otherwise simply copy */ + + /*memcpy(data,block,iLBCenc_inst->blockl*sizeof(float));*/ + + /* LPC of hp filtered input data */ + + LPCencode(syntdenum, weightdenum, lsf_i, data, iLBCenc_inst); + + + /* inverse filter to get residual */ + + for (n=0; n<iLBCenc_inst->nsub; n++) { + anaFilter(&data[n*SUBL], &syntdenum[n*(LPC_FILTERORDER+1)], + SUBL, &residual[n*SUBL], iLBCenc_inst->anaMem); + } + + /* find state location */ + + start = FrameClassify(iLBCenc_inst, residual); + + /* check if state should be in first or last part of the + two subframes */ + + diff = STATE_LEN - iLBCenc_inst->state_short_len; + en1 = 0; + index = (start-1)*SUBL; + + + +Andersen, et al. Experimental [Page 55] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + for (i = 0; i < iLBCenc_inst->state_short_len; i++) { + en1 += residual[index+i]*residual[index+i]; + } + en2 = 0; + index = (start-1)*SUBL+diff; + for (i = 0; i < iLBCenc_inst->state_short_len; i++) { + en2 += residual[index+i]*residual[index+i]; + } + + + if (en1 > en2) { + state_first = 1; + start_pos = (start-1)*SUBL; + } else { + state_first = 0; + start_pos = (start-1)*SUBL + diff; + } + + /* scalar quantization of state */ + + StateSearchW(iLBCenc_inst, &residual[start_pos], + &syntdenum[(start-1)*(LPC_FILTERORDER+1)], + &weightdenum[(start-1)*(LPC_FILTERORDER+1)], &idxForMax, + idxVec, iLBCenc_inst->state_short_len, state_first); + + StateConstructW(idxForMax, idxVec, + &syntdenum[(start-1)*(LPC_FILTERORDER+1)], + &decresidual[start_pos], iLBCenc_inst->state_short_len); + + /* predictive quantization in state */ + + if (state_first) { /* put adaptive part in the end */ + + /* setup memory */ + + memset(mem, 0, + (CB_MEML-iLBCenc_inst->state_short_len)*sizeof(float)); + memcpy(mem+CB_MEML-iLBCenc_inst->state_short_len, + decresidual+start_pos, + iLBCenc_inst->state_short_len*sizeof(float)); + memset(weightState, 0, LPC_FILTERORDER*sizeof(float)); + + /* encode sub-frames */ + + iCBSearch(iLBCenc_inst, extra_cb_index, extra_gain_index, + &residual[start_pos+iLBCenc_inst->state_short_len], + mem+CB_MEML-stMemLTbl, + stMemLTbl, diff, CB_NSTAGES, + + + +Andersen, et al. Experimental [Page 56] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + &weightdenum[start*(LPC_FILTERORDER+1)], + weightState, 0); + + /* construct decoded vector */ + + iCBConstruct( + &decresidual[start_pos+iLBCenc_inst->state_short_len], + extra_cb_index, extra_gain_index, + mem+CB_MEML-stMemLTbl, + stMemLTbl, diff, CB_NSTAGES); + + } + else { /* put adaptive part in the beginning */ + + /* create reversed vectors for prediction */ + + for (k=0; k<diff; k++) { + reverseResidual[k] = residual[(start+1)*SUBL-1 + -(k+iLBCenc_inst->state_short_len)]; + } + + /* setup memory */ + + meml_gotten = iLBCenc_inst->state_short_len; + for (k=0; k<meml_gotten; k++) { + mem[CB_MEML-1-k] = decresidual[start_pos + k]; + } + memset(mem, 0, (CB_MEML-k)*sizeof(float)); + memset(weightState, 0, LPC_FILTERORDER*sizeof(float)); + + /* encode sub-frames */ + + iCBSearch(iLBCenc_inst, extra_cb_index, extra_gain_index, + reverseResidual, mem+CB_MEML-stMemLTbl, stMemLTbl, + diff, CB_NSTAGES, + &weightdenum[(start-1)*(LPC_FILTERORDER+1)], + weightState, 0); + + /* construct decoded vector */ + + iCBConstruct(reverseDecresidual, extra_cb_index, + extra_gain_index, mem+CB_MEML-stMemLTbl, stMemLTbl, + diff, CB_NSTAGES); + + /* get decoded residual from reversed vector */ + + for (k=0; k<diff; k++) { + decresidual[start_pos-1-k] = reverseDecresidual[k]; + + + +Andersen, et al. Experimental [Page 57] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + } + } + + /* counter for predicted sub-frames */ + + subcount=0; + + /* forward prediction of sub-frames */ + + Nfor = iLBCenc_inst->nsub-start-1; + + + if ( Nfor > 0 ) { + + /* setup memory */ + + memset(mem, 0, (CB_MEML-STATE_LEN)*sizeof(float)); + memcpy(mem+CB_MEML-STATE_LEN, decresidual+(start-1)*SUBL, + STATE_LEN*sizeof(float)); + memset(weightState, 0, LPC_FILTERORDER*sizeof(float)); + + /* loop over sub-frames to encode */ + + for (subframe=0; subframe<Nfor; subframe++) { + + /* encode sub-frame */ + + iCBSearch(iLBCenc_inst, cb_index+subcount*CB_NSTAGES, + gain_index+subcount*CB_NSTAGES, + &residual[(start+1+subframe)*SUBL], + mem+CB_MEML-memLfTbl[subcount], + memLfTbl[subcount], SUBL, CB_NSTAGES, + &weightdenum[(start+1+subframe)* + (LPC_FILTERORDER+1)], + weightState, subcount+1); + + /* construct decoded vector */ + + iCBConstruct(&decresidual[(start+1+subframe)*SUBL], + cb_index+subcount*CB_NSTAGES, + gain_index+subcount*CB_NSTAGES, + mem+CB_MEML-memLfTbl[subcount], + memLfTbl[subcount], SUBL, CB_NSTAGES); + + /* update memory */ + + memcpy(mem, mem+SUBL, (CB_MEML-SUBL)*sizeof(float)); + memcpy(mem+CB_MEML-SUBL, + + + +Andersen, et al. Experimental [Page 58] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + &decresidual[(start+1+subframe)*SUBL], + SUBL*sizeof(float)); + memset(weightState, 0, LPC_FILTERORDER*sizeof(float)); + + subcount++; + } + } + + + /* backward prediction of sub-frames */ + + Nback = start-1; + + + if ( Nback > 0 ) { + + /* create reverse order vectors */ + + for (n=0; n<Nback; n++) { + for (k=0; k<SUBL; k++) { + reverseResidual[n*SUBL+k] = + residual[(start-1)*SUBL-1-n*SUBL-k]; + reverseDecresidual[n*SUBL+k] = + decresidual[(start-1)*SUBL-1-n*SUBL-k]; + } + } + + /* setup memory */ + + meml_gotten = SUBL*(iLBCenc_inst->nsub+1-start); + + + if ( meml_gotten > CB_MEML ) { + meml_gotten=CB_MEML; + } + for (k=0; k<meml_gotten; k++) { + mem[CB_MEML-1-k] = decresidual[(start-1)*SUBL + k]; + } + memset(mem, 0, (CB_MEML-k)*sizeof(float)); + memset(weightState, 0, LPC_FILTERORDER*sizeof(float)); + + /* loop over sub-frames to encode */ + + for (subframe=0; subframe<Nback; subframe++) { + + /* encode sub-frame */ + + iCBSearch(iLBCenc_inst, cb_index+subcount*CB_NSTAGES, + + + +Andersen, et al. Experimental [Page 59] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + gain_index+subcount*CB_NSTAGES, + &reverseResidual[subframe*SUBL], + mem+CB_MEML-memLfTbl[subcount], + memLfTbl[subcount], SUBL, CB_NSTAGES, + &weightdenum[(start-2-subframe)* + (LPC_FILTERORDER+1)], + weightState, subcount+1); + + /* construct decoded vector */ + + iCBConstruct(&reverseDecresidual[subframe*SUBL], + cb_index+subcount*CB_NSTAGES, + gain_index+subcount*CB_NSTAGES, + mem+CB_MEML-memLfTbl[subcount], + memLfTbl[subcount], SUBL, CB_NSTAGES); + + /* update memory */ + + memcpy(mem, mem+SUBL, (CB_MEML-SUBL)*sizeof(float)); + memcpy(mem+CB_MEML-SUBL, + &reverseDecresidual[subframe*SUBL], + SUBL*sizeof(float)); + memset(weightState, 0, LPC_FILTERORDER*sizeof(float)); + + subcount++; + + } + + /* get decoded residual from reversed vector */ + + for (i=0; i<SUBL*Nback; i++) { + decresidual[SUBL*Nback - i - 1] = + reverseDecresidual[i]; + } + } + /* end encoding part */ + + /* adjust index */ + index_conv_enc(cb_index); + + /* pack bytes */ + + pbytes=bytes; + pos=0; + + /* loop over the 3 ULP classes */ + + for (ulp=0; ulp<3; ulp++) { + + + +Andersen, et al. Experimental [Page 60] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + + /* LSF */ + for (k=0; k<LSF_NSPLIT*iLBCenc_inst->lpc_n; k++) { + packsplit(&lsf_i[k], &firstpart, &lsf_i[k], + iLBCenc_inst->ULP_inst->lsf_bits[k][ulp], + iLBCenc_inst->ULP_inst->lsf_bits[k][ulp]+ + iLBCenc_inst->ULP_inst->lsf_bits[k][ulp+1]+ + iLBCenc_inst->ULP_inst->lsf_bits[k][ulp+2]); + dopack( &pbytes, firstpart, + iLBCenc_inst->ULP_inst->lsf_bits[k][ulp], &pos); + } + + /* Start block info */ + + packsplit(&start, &firstpart, &start, + iLBCenc_inst->ULP_inst->start_bits[ulp], + iLBCenc_inst->ULP_inst->start_bits[ulp]+ + iLBCenc_inst->ULP_inst->start_bits[ulp+1]+ + iLBCenc_inst->ULP_inst->start_bits[ulp+2]); + dopack( &pbytes, firstpart, + iLBCenc_inst->ULP_inst->start_bits[ulp], &pos); + + packsplit(&state_first, &firstpart, &state_first, + iLBCenc_inst->ULP_inst->startfirst_bits[ulp], + iLBCenc_inst->ULP_inst->startfirst_bits[ulp]+ + iLBCenc_inst->ULP_inst->startfirst_bits[ulp+1]+ + iLBCenc_inst->ULP_inst->startfirst_bits[ulp+2]); + dopack( &pbytes, firstpart, + iLBCenc_inst->ULP_inst->startfirst_bits[ulp], &pos); + + packsplit(&idxForMax, &firstpart, &idxForMax, + iLBCenc_inst->ULP_inst->scale_bits[ulp], + iLBCenc_inst->ULP_inst->scale_bits[ulp]+ + iLBCenc_inst->ULP_inst->scale_bits[ulp+1]+ + iLBCenc_inst->ULP_inst->scale_bits[ulp+2]); + dopack( &pbytes, firstpart, + iLBCenc_inst->ULP_inst->scale_bits[ulp], &pos); + + for (k=0; k<iLBCenc_inst->state_short_len; k++) { + packsplit(idxVec+k, &firstpart, idxVec+k, + iLBCenc_inst->ULP_inst->state_bits[ulp], + iLBCenc_inst->ULP_inst->state_bits[ulp]+ + iLBCenc_inst->ULP_inst->state_bits[ulp+1]+ + iLBCenc_inst->ULP_inst->state_bits[ulp+2]); + dopack( &pbytes, firstpart, + iLBCenc_inst->ULP_inst->state_bits[ulp], &pos); + } + + + + +Andersen, et al. Experimental [Page 61] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + /* 23/22 (20ms/30ms) sample block */ + + for (k=0;k<CB_NSTAGES;k++) { + packsplit(extra_cb_index+k, &firstpart, + extra_cb_index+k, + iLBCenc_inst->ULP_inst->extra_cb_index[k][ulp], + iLBCenc_inst->ULP_inst->extra_cb_index[k][ulp]+ + iLBCenc_inst->ULP_inst->extra_cb_index[k][ulp+1]+ + iLBCenc_inst->ULP_inst->extra_cb_index[k][ulp+2]); + dopack( &pbytes, firstpart, + iLBCenc_inst->ULP_inst->extra_cb_index[k][ulp], + &pos); + } + + for (k=0;k<CB_NSTAGES;k++) { + packsplit(extra_gain_index+k, &firstpart, + extra_gain_index+k, + iLBCenc_inst->ULP_inst->extra_cb_gain[k][ulp], + iLBCenc_inst->ULP_inst->extra_cb_gain[k][ulp]+ + iLBCenc_inst->ULP_inst->extra_cb_gain[k][ulp+1]+ + iLBCenc_inst->ULP_inst->extra_cb_gain[k][ulp+2]); + dopack( &pbytes, firstpart, + iLBCenc_inst->ULP_inst->extra_cb_gain[k][ulp], + &pos); + } + + /* The two/four (20ms/30ms) 40 sample sub-blocks */ + + for (i=0; i<iLBCenc_inst->nasub; i++) { + for (k=0; k<CB_NSTAGES; k++) { + packsplit(cb_index+i*CB_NSTAGES+k, &firstpart, + cb_index+i*CB_NSTAGES+k, + iLBCenc_inst->ULP_inst->cb_index[i][k][ulp], + iLBCenc_inst->ULP_inst->cb_index[i][k][ulp]+ + iLBCenc_inst->ULP_inst->cb_index[i][k][ulp+1]+ + iLBCenc_inst->ULP_inst->cb_index[i][k][ulp+2]); + dopack( &pbytes, firstpart, + iLBCenc_inst->ULP_inst->cb_index[i][k][ulp], + &pos); + } + } + + for (i=0; i<iLBCenc_inst->nasub; i++) { + for (k=0; k<CB_NSTAGES; k++) { + packsplit(gain_index+i*CB_NSTAGES+k, &firstpart, + gain_index+i*CB_NSTAGES+k, + iLBCenc_inst->ULP_inst->cb_gain[i][k][ulp], + iLBCenc_inst->ULP_inst->cb_gain[i][k][ulp]+ + + + +Andersen, et al. Experimental [Page 62] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + iLBCenc_inst->ULP_inst->cb_gain[i][k][ulp+1]+ + iLBCenc_inst->ULP_inst->cb_gain[i][k][ulp+2]); + dopack( &pbytes, firstpart, + iLBCenc_inst->ULP_inst->cb_gain[i][k][ulp], + &pos); + } + } + } + + /* set the last bit to zero (otherwise the decoder + will treat it as a lost frame) */ + dopack( &pbytes, 0, 1, &pos); + } + +A.4. iLBC_decode.h + + /****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + iLBC_decode.h + + Copyright (C) The Internet Society (2004). + All Rights Reserved. + + ******************************************************************/ + + #ifndef __iLBC_ILBCDECODE_H + #define __iLBC_ILBCDECODE_H + + #include "iLBC_define.h" + + short initDecode( /* (o) Number of decoded + samples */ + iLBC_Dec_Inst_t *iLBCdec_inst, /* (i/o) Decoder instance */ + int mode, /* (i) frame size mode */ + int use_enhancer /* (i) 1 to use enhancer + 0 to run without + enhancer */ + ); + + void iLBC_decode( + float *decblock, /* (o) decoded signal block */ + unsigned char *bytes, /* (i) encoded signal bits */ + iLBC_Dec_Inst_t *iLBCdec_inst, /* (i/o) the decoder state + structure */ + int mode /* (i) 0: bad packet, PLC, + 1: normal */ + + + +Andersen, et al. Experimental [Page 63] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + ); + + #endif + +A.5. iLBC_decode.c + + /****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + iLBC_decode.c + + Copyright (C) The Internet Society (2004). + All Rights Reserved. + + ******************************************************************/ + + #include <math.h> + #include <stdlib.h> + + #include "iLBC_define.h" + #include "StateConstructW.h" + #include "LPCdecode.h" + #include "iCBConstruct.h" + #include "doCPLC.h" + #include "helpfun.h" + #include "constants.h" + #include "packing.h" + #include "string.h" + #include "enhancer.h" + #include "hpOutput.h" + #include "syntFilter.h" + + /*----------------------------------------------------------------* + * Initiation of decoder instance. + *---------------------------------------------------------------*/ + + short initDecode( /* (o) Number of decoded + samples */ + iLBC_Dec_Inst_t *iLBCdec_inst, /* (i/o) Decoder instance */ + int mode, /* (i) frame size mode */ + int use_enhancer /* (i) 1 to use enhancer + 0 to run without + enhancer */ + ){ + int i; + + iLBCdec_inst->mode = mode; + + + +Andersen, et al. Experimental [Page 64] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + if (mode==30) { + iLBCdec_inst->blockl = BLOCKL_30MS; + iLBCdec_inst->nsub = NSUB_30MS; + iLBCdec_inst->nasub = NASUB_30MS; + iLBCdec_inst->lpc_n = LPC_N_30MS; + iLBCdec_inst->no_of_bytes = NO_OF_BYTES_30MS; + iLBCdec_inst->no_of_words = NO_OF_WORDS_30MS; + iLBCdec_inst->state_short_len=STATE_SHORT_LEN_30MS; + /* ULP init */ + iLBCdec_inst->ULP_inst=&ULP_30msTbl; + } + else if (mode==20) { + iLBCdec_inst->blockl = BLOCKL_20MS; + iLBCdec_inst->nsub = NSUB_20MS; + iLBCdec_inst->nasub = NASUB_20MS; + iLBCdec_inst->lpc_n = LPC_N_20MS; + iLBCdec_inst->no_of_bytes = NO_OF_BYTES_20MS; + iLBCdec_inst->no_of_words = NO_OF_WORDS_20MS; + iLBCdec_inst->state_short_len=STATE_SHORT_LEN_20MS; + /* ULP init */ + iLBCdec_inst->ULP_inst=&ULP_20msTbl; + } + else { + exit(2); + } + + memset(iLBCdec_inst->syntMem, 0, + LPC_FILTERORDER*sizeof(float)); + memcpy((*iLBCdec_inst).lsfdeqold, lsfmeanTbl, + LPC_FILTERORDER*sizeof(float)); + + memset(iLBCdec_inst->old_syntdenum, 0, + ((LPC_FILTERORDER + 1)*NSUB_MAX)*sizeof(float)); + for (i=0; i<NSUB_MAX; i++) + iLBCdec_inst->old_syntdenum[i*(LPC_FILTERORDER+1)]=1.0; + + iLBCdec_inst->last_lag = 20; + + iLBCdec_inst->prevLag = 120; + iLBCdec_inst->per = 0.0; + iLBCdec_inst->consPLICount = 0; + iLBCdec_inst->prevPLI = 0; + iLBCdec_inst->prevLpc[0] = 1.0; + memset(iLBCdec_inst->prevLpc+1,0, + LPC_FILTERORDER*sizeof(float)); + memset(iLBCdec_inst->prevResidual, 0, BLOCKL_MAX*sizeof(float)); + iLBCdec_inst->seed=777; + + + + +Andersen, et al. Experimental [Page 65] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + memset(iLBCdec_inst->hpomem, 0, 4*sizeof(float)); + + iLBCdec_inst->use_enhancer = use_enhancer; + memset(iLBCdec_inst->enh_buf, 0, ENH_BUFL*sizeof(float)); + for (i=0;i<ENH_NBLOCKS_TOT;i++) + iLBCdec_inst->enh_period[i]=(float)40.0; + + iLBCdec_inst->prev_enh_pl = 0; + + return (iLBCdec_inst->blockl); + } + + /*----------------------------------------------------------------* + * frame residual decoder function (subrutine to iLBC_decode) + *---------------------------------------------------------------*/ + + void Decode( + iLBC_Dec_Inst_t *iLBCdec_inst, /* (i/o) the decoder state + structure */ + float *decresidual, /* (o) decoded residual frame */ + int start, /* (i) location of start + state */ + int idxForMax, /* (i) codebook index for the + maximum value */ + int *idxVec, /* (i) codebook indexes for the + samples in the start + state */ + float *syntdenum, /* (i) the decoded synthesis + filter coefficients */ + int *cb_index, /* (i) the indexes for the + adaptive codebook */ + int *gain_index, /* (i) the indexes for the + corresponding gains */ + int *extra_cb_index, /* (i) the indexes for the + adaptive codebook part + of start state */ + int *extra_gain_index, /* (i) the indexes for the + corresponding gains */ + int state_first /* (i) 1 if non adaptive part + of start state comes + first 0 if that part + comes last */ + ){ + float reverseDecresidual[BLOCKL_MAX], mem[CB_MEML]; + int k, meml_gotten, Nfor, Nback, i; + int diff, start_pos; + int subcount, subframe; + + + + +Andersen, et al. Experimental [Page 66] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + diff = STATE_LEN - iLBCdec_inst->state_short_len; + + if (state_first == 1) { + start_pos = (start-1)*SUBL; + } else { + start_pos = (start-1)*SUBL + diff; + } + + /* decode scalar part of start state */ + + StateConstructW(idxForMax, idxVec, + &syntdenum[(start-1)*(LPC_FILTERORDER+1)], + &decresidual[start_pos], iLBCdec_inst->state_short_len); + + + if (state_first) { /* put adaptive part in the end */ + + /* setup memory */ + + memset(mem, 0, + (CB_MEML-iLBCdec_inst->state_short_len)*sizeof(float)); + memcpy(mem+CB_MEML-iLBCdec_inst->state_short_len, + decresidual+start_pos, + iLBCdec_inst->state_short_len*sizeof(float)); + + /* construct decoded vector */ + + iCBConstruct( + &decresidual[start_pos+iLBCdec_inst->state_short_len], + extra_cb_index, extra_gain_index, mem+CB_MEML-stMemLTbl, + stMemLTbl, diff, CB_NSTAGES); + + } + else {/* put adaptive part in the beginning */ + + /* create reversed vectors for prediction */ + + for (k=0; k<diff; k++) { + reverseDecresidual[k] = + decresidual[(start+1)*SUBL-1- + (k+iLBCdec_inst->state_short_len)]; + } + + /* setup memory */ + + meml_gotten = iLBCdec_inst->state_short_len; + for (k=0; k<meml_gotten; k++){ + mem[CB_MEML-1-k] = decresidual[start_pos + k]; + + + +Andersen, et al. Experimental [Page 67] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + } + memset(mem, 0, (CB_MEML-k)*sizeof(float)); + + /* construct decoded vector */ + + iCBConstruct(reverseDecresidual, extra_cb_index, + extra_gain_index, mem+CB_MEML-stMemLTbl, stMemLTbl, + diff, CB_NSTAGES); + + /* get decoded residual from reversed vector */ + + for (k=0; k<diff; k++) { + decresidual[start_pos-1-k] = reverseDecresidual[k]; + } + } + + /* counter for predicted sub-frames */ + + subcount=0; + + /* forward prediction of sub-frames */ + + Nfor = iLBCdec_inst->nsub-start-1; + + if ( Nfor > 0 ){ + + /* setup memory */ + + memset(mem, 0, (CB_MEML-STATE_LEN)*sizeof(float)); + memcpy(mem+CB_MEML-STATE_LEN, decresidual+(start-1)*SUBL, + STATE_LEN*sizeof(float)); + + /* loop over sub-frames to encode */ + + for (subframe=0; subframe<Nfor; subframe++) { + + /* construct decoded vector */ + + iCBConstruct(&decresidual[(start+1+subframe)*SUBL], + cb_index+subcount*CB_NSTAGES, + gain_index+subcount*CB_NSTAGES, + mem+CB_MEML-memLfTbl[subcount], + memLfTbl[subcount], SUBL, CB_NSTAGES); + + /* update memory */ + + memcpy(mem, mem+SUBL, (CB_MEML-SUBL)*sizeof(float)); + memcpy(mem+CB_MEML-SUBL, + + + +Andersen, et al. Experimental [Page 68] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + &decresidual[(start+1+subframe)*SUBL], + SUBL*sizeof(float)); + + subcount++; + + } + + } + + /* backward prediction of sub-frames */ + + Nback = start-1; + + if ( Nback > 0 ) { + + /* setup memory */ + + meml_gotten = SUBL*(iLBCdec_inst->nsub+1-start); + + if ( meml_gotten > CB_MEML ) { + meml_gotten=CB_MEML; + } + for (k=0; k<meml_gotten; k++) { + mem[CB_MEML-1-k] = decresidual[(start-1)*SUBL + k]; + } + memset(mem, 0, (CB_MEML-k)*sizeof(float)); + + /* loop over subframes to decode */ + + for (subframe=0; subframe<Nback; subframe++) { + + /* construct decoded vector */ + + iCBConstruct(&reverseDecresidual[subframe*SUBL], + cb_index+subcount*CB_NSTAGES, + gain_index+subcount*CB_NSTAGES, + mem+CB_MEML-memLfTbl[subcount], memLfTbl[subcount], + SUBL, CB_NSTAGES); + + /* update memory */ + + memcpy(mem, mem+SUBL, (CB_MEML-SUBL)*sizeof(float)); + memcpy(mem+CB_MEML-SUBL, + &reverseDecresidual[subframe*SUBL], + SUBL*sizeof(float)); + + subcount++; + } + + + +Andersen, et al. Experimental [Page 69] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + /* get decoded residual from reversed vector */ + + for (i=0; i<SUBL*Nback; i++) + decresidual[SUBL*Nback - i - 1] = + reverseDecresidual[i]; + } + } + + /*----------------------------------------------------------------* + * main decoder function + *---------------------------------------------------------------*/ + + void iLBC_decode( + float *decblock, /* (o) decoded signal block */ + unsigned char *bytes, /* (i) encoded signal bits */ + iLBC_Dec_Inst_t *iLBCdec_inst, /* (i/o) the decoder state + structure */ + int mode /* (i) 0: bad packet, PLC, + 1: normal */ + ){ + float data[BLOCKL_MAX]; + float lsfdeq[LPC_FILTERORDER*LPC_N_MAX]; + float PLCresidual[BLOCKL_MAX], PLClpc[LPC_FILTERORDER + 1]; + float zeros[BLOCKL_MAX], one[LPC_FILTERORDER + 1]; + int k, i, start, idxForMax, pos, lastpart, ulp; + int lag, ilag; + float cc, maxcc; + int idxVec[STATE_LEN]; + int check; + int gain_index[NASUB_MAX*CB_NSTAGES], + extra_gain_index[CB_NSTAGES]; + int cb_index[CB_NSTAGES*NASUB_MAX], extra_cb_index[CB_NSTAGES]; + int lsf_i[LSF_NSPLIT*LPC_N_MAX]; + int state_first; + int last_bit; + unsigned char *pbytes; + float weightdenum[(LPC_FILTERORDER + 1)*NSUB_MAX]; + int order_plus_one; + float syntdenum[NSUB_MAX*(LPC_FILTERORDER+1)]; + float decresidual[BLOCKL_MAX]; + + if (mode>0) { /* the data are good */ + + /* decode data */ + + pbytes=bytes; + pos=0; + + + + +Andersen, et al. Experimental [Page 70] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + /* Set everything to zero before decoding */ + + for (k=0; k<LSF_NSPLIT*LPC_N_MAX; k++) { + lsf_i[k]=0; + } + start=0; + state_first=0; + idxForMax=0; + for (k=0; k<iLBCdec_inst->state_short_len; k++) { + idxVec[k]=0; + } + for (k=0; k<CB_NSTAGES; k++) { + extra_cb_index[k]=0; + } + for (k=0; k<CB_NSTAGES; k++) { + extra_gain_index[k]=0; + } + for (i=0; i<iLBCdec_inst->nasub; i++) { + for (k=0; k<CB_NSTAGES; k++) { + cb_index[i*CB_NSTAGES+k]=0; + } + } + for (i=0; i<iLBCdec_inst->nasub; i++) { + for (k=0; k<CB_NSTAGES; k++) { + gain_index[i*CB_NSTAGES+k]=0; + } + } + + /* loop over ULP classes */ + + for (ulp=0; ulp<3; ulp++) { + + /* LSF */ + for (k=0; k<LSF_NSPLIT*iLBCdec_inst->lpc_n; k++){ + unpack( &pbytes, &lastpart, + iLBCdec_inst->ULP_inst->lsf_bits[k][ulp], &pos); + packcombine(&lsf_i[k], lastpart, + iLBCdec_inst->ULP_inst->lsf_bits[k][ulp]); + } + + /* Start block info */ + + unpack( &pbytes, &lastpart, + iLBCdec_inst->ULP_inst->start_bits[ulp], &pos); + packcombine(&start, lastpart, + iLBCdec_inst->ULP_inst->start_bits[ulp]); + + unpack( &pbytes, &lastpart, + + + +Andersen, et al. Experimental [Page 71] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + iLBCdec_inst->ULP_inst->startfirst_bits[ulp], &pos); + packcombine(&state_first, lastpart, + iLBCdec_inst->ULP_inst->startfirst_bits[ulp]); + + unpack( &pbytes, &lastpart, + iLBCdec_inst->ULP_inst->scale_bits[ulp], &pos); + packcombine(&idxForMax, lastpart, + iLBCdec_inst->ULP_inst->scale_bits[ulp]); + + for (k=0; k<iLBCdec_inst->state_short_len; k++) { + unpack( &pbytes, &lastpart, + iLBCdec_inst->ULP_inst->state_bits[ulp], &pos); + packcombine(idxVec+k, lastpart, + iLBCdec_inst->ULP_inst->state_bits[ulp]); + } + + /* 23/22 (20ms/30ms) sample block */ + + for (k=0; k<CB_NSTAGES; k++) { + unpack( &pbytes, &lastpart, + iLBCdec_inst->ULP_inst->extra_cb_index[k][ulp], + &pos); + packcombine(extra_cb_index+k, lastpart, + iLBCdec_inst->ULP_inst->extra_cb_index[k][ulp]); + } + for (k=0; k<CB_NSTAGES; k++) { + unpack( &pbytes, &lastpart, + iLBCdec_inst->ULP_inst->extra_cb_gain[k][ulp], + &pos); + packcombine(extra_gain_index+k, lastpart, + iLBCdec_inst->ULP_inst->extra_cb_gain[k][ulp]); + } + + /* The two/four (20ms/30ms) 40 sample sub-blocks */ + + for (i=0; i<iLBCdec_inst->nasub; i++) { + for (k=0; k<CB_NSTAGES; k++) { + unpack( &pbytes, &lastpart, + iLBCdec_inst->ULP_inst->cb_index[i][k][ulp], + &pos); + packcombine(cb_index+i*CB_NSTAGES+k, lastpart, + iLBCdec_inst->ULP_inst->cb_index[i][k][ulp]); + } + } + + for (i=0; i<iLBCdec_inst->nasub; i++) { + for (k=0; k<CB_NSTAGES; k++) { + unpack( &pbytes, &lastpart, + + + +Andersen, et al. Experimental [Page 72] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + iLBCdec_inst->ULP_inst->cb_gain[i][k][ulp], + &pos); + packcombine(gain_index+i*CB_NSTAGES+k, lastpart, + iLBCdec_inst->ULP_inst->cb_gain[i][k][ulp]); + } + } + } + /* Extract last bit. If it is 1 this indicates an + empty/lost frame */ + unpack( &pbytes, &last_bit, 1, &pos); + + /* Check for bit errors or empty/lost frames */ + if (start<1) + mode = 0; + if (iLBCdec_inst->mode==20 && start>3) + mode = 0; + if (iLBCdec_inst->mode==30 && start>5) + mode = 0; + if (last_bit==1) + mode = 0; + + if (mode==1) { /* No bit errors was detected, + continue decoding */ + + /* adjust index */ + index_conv_dec(cb_index); + + /* decode the lsf */ + + SimplelsfDEQ(lsfdeq, lsf_i, iLBCdec_inst->lpc_n); + check=LSF_check(lsfdeq, LPC_FILTERORDER, + iLBCdec_inst->lpc_n); + DecoderInterpolateLSF(syntdenum, weightdenum, + lsfdeq, LPC_FILTERORDER, iLBCdec_inst); + + Decode(iLBCdec_inst, decresidual, start, idxForMax, + idxVec, syntdenum, cb_index, gain_index, + extra_cb_index, extra_gain_index, + state_first); + + /* preparing the plc for a future loss! */ + + doThePLC(PLCresidual, PLClpc, 0, decresidual, + syntdenum + + (LPC_FILTERORDER + 1)*(iLBCdec_inst->nsub - 1), + (*iLBCdec_inst).last_lag, iLBCdec_inst); + + + + + +Andersen, et al. Experimental [Page 73] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + memcpy(decresidual, PLCresidual, + iLBCdec_inst->blockl*sizeof(float)); + } + + } + + if (mode == 0) { + /* the data is bad (either a PLC call + * was made or a severe bit error was detected) + */ + + /* packet loss conceal */ + + memset(zeros, 0, BLOCKL_MAX*sizeof(float)); + + one[0] = 1; + memset(one+1, 0, LPC_FILTERORDER*sizeof(float)); + + start=0; + + doThePLC(PLCresidual, PLClpc, 1, zeros, one, + (*iLBCdec_inst).last_lag, iLBCdec_inst); + memcpy(decresidual, PLCresidual, + iLBCdec_inst->blockl*sizeof(float)); + + order_plus_one = LPC_FILTERORDER + 1; + for (i = 0; i < iLBCdec_inst->nsub; i++) { + memcpy(syntdenum+(i*order_plus_one), PLClpc, + order_plus_one*sizeof(float)); + } + } + + if (iLBCdec_inst->use_enhancer == 1) { + + /* post filtering */ + + iLBCdec_inst->last_lag = + enhancerInterface(data, decresidual, iLBCdec_inst); + + /* synthesis filtering */ + + if (iLBCdec_inst->mode==20) { + /* Enhancer has 40 samples delay */ + i=0; + syntFilter(data + i*SUBL, + iLBCdec_inst->old_syntdenum + + (i+iLBCdec_inst->nsub-1)*(LPC_FILTERORDER+1), + SUBL, iLBCdec_inst->syntMem); + + + +Andersen, et al. Experimental [Page 74] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + for (i=1; i < iLBCdec_inst->nsub; i++) { + syntFilter(data + i*SUBL, + syntdenum + (i-1)*(LPC_FILTERORDER+1), + SUBL, iLBCdec_inst->syntMem); + } + } else if (iLBCdec_inst->mode==30) { + /* Enhancer has 80 samples delay */ + for (i=0; i < 2; i++) { + syntFilter(data + i*SUBL, + iLBCdec_inst->old_syntdenum + + (i+iLBCdec_inst->nsub-2)*(LPC_FILTERORDER+1), + SUBL, iLBCdec_inst->syntMem); + } + for (i=2; i < iLBCdec_inst->nsub; i++) { + syntFilter(data + i*SUBL, + syntdenum + (i-2)*(LPC_FILTERORDER+1), SUBL, + iLBCdec_inst->syntMem); + } + } + + } else { + + /* Find last lag */ + lag = 20; + maxcc = xCorrCoef(&decresidual[BLOCKL_MAX-ENH_BLOCKL], + &decresidual[BLOCKL_MAX-ENH_BLOCKL-lag], ENH_BLOCKL); + + for (ilag=21; ilag<120; ilag++) { + cc = xCorrCoef(&decresidual[BLOCKL_MAX-ENH_BLOCKL], + &decresidual[BLOCKL_MAX-ENH_BLOCKL-ilag], + ENH_BLOCKL); + + if (cc > maxcc) { + maxcc = cc; + lag = ilag; + } + } + iLBCdec_inst->last_lag = lag; + + /* copy data and run synthesis filter */ + + memcpy(data, decresidual, + iLBCdec_inst->blockl*sizeof(float)); + for (i=0; i < iLBCdec_inst->nsub; i++) { + syntFilter(data + i*SUBL, + syntdenum + i*(LPC_FILTERORDER+1), SUBL, + iLBCdec_inst->syntMem); + } + + + +Andersen, et al. Experimental [Page 75] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + } + + /* high pass filtering on output if desired, otherwise + copy to out */ + + hpOutput(data, iLBCdec_inst->blockl, + decblock,iLBCdec_inst->hpomem); + + /* memcpy(decblock,data,iLBCdec_inst->blockl*sizeof(float));*/ + + memcpy(iLBCdec_inst->old_syntdenum, syntdenum, + + iLBCdec_inst->nsub*(LPC_FILTERORDER+1)*sizeof(float)); + + iLBCdec_inst->prev_enh_pl=0; + + if (mode==0) { /* PLC was used */ + iLBCdec_inst->prev_enh_pl=1; + } + } + +A.6. iLBC_define.h + + /****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + iLBC_define.h + + Copyright (C) The Internet Society (2004). + All Rights Reserved. + + ******************************************************************/ + #include <string.h> + + #ifndef __iLBC_ILBCDEFINE_H + #define __iLBC_ILBCDEFINE_H + + /* general codec settings */ + + #define FS (float)8000.0 + #define BLOCKL_20MS 160 + #define BLOCKL_30MS 240 + #define BLOCKL_MAX 240 + #define NSUB_20MS 4 + #define NSUB_30MS 6 + #define NSUB_MAX 6 + #define NASUB_20MS 2 + + + +Andersen, et al. Experimental [Page 76] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + #define NASUB_30MS 4 + #define NASUB_MAX 4 + #define SUBL 40 + #define STATE_LEN 80 + #define STATE_SHORT_LEN_30MS 58 + #define STATE_SHORT_LEN_20MS 57 + + /* LPC settings */ + + #define LPC_FILTERORDER 10 + #define LPC_CHIRP_SYNTDENUM (float)0.9025 + #define LPC_CHIRP_WEIGHTDENUM (float)0.4222 + #define LPC_LOOKBACK 60 + #define LPC_N_20MS 1 + #define LPC_N_30MS 2 + #define LPC_N_MAX 2 + #define LPC_ASYMDIFF 20 + #define LPC_BW (float)60.0 + #define LPC_WN (float)1.0001 + #define LSF_NSPLIT 3 + #define LSF_NUMBER_OF_STEPS 4 + #define LPC_HALFORDER (LPC_FILTERORDER/2) + + /* cb settings */ + + #define CB_NSTAGES 3 + #define CB_EXPAND 2 + #define CB_MEML 147 + #define CB_FILTERLEN 2*4 + #define CB_HALFFILTERLEN 4 + #define CB_RESRANGE 34 + #define CB_MAXGAIN (float)1.3 + + /* enhancer */ + + #define ENH_BLOCKL 80 /* block length */ + #define ENH_BLOCKL_HALF (ENH_BLOCKL/2) + #define ENH_HL 3 /* 2*ENH_HL+1 is number blocks + in said second sequence */ + #define ENH_SLOP 2 /* max difference estimated and + correct pitch period */ + #define ENH_PLOCSL 20 /* pitch-estimates and pitch- + locations buffer length */ + #define ENH_OVERHANG 2 + #define ENH_UPS0 4 /* upsampling rate */ + #define ENH_FL0 3 /* 2*FLO+1 is the length of + each filter */ + #define ENH_VECTL (ENH_BLOCKL+2*ENH_FL0) + + + +Andersen, et al. Experimental [Page 77] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + #define ENH_CORRDIM (2*ENH_SLOP+1) + #define ENH_NBLOCKS (BLOCKL_MAX/ENH_BLOCKL) + #define ENH_NBLOCKS_EXTRA 5 + #define ENH_NBLOCKS_TOT 8 /* ENH_NBLOCKS + + ENH_NBLOCKS_EXTRA */ + #define ENH_BUFL (ENH_NBLOCKS_TOT)*ENH_BLOCKL + #define ENH_ALPHA0 (float)0.05 + + /* Down sampling */ + + #define FILTERORDER_DS 7 + #define DELAY_DS 3 + #define FACTOR_DS 2 + + /* bit stream defs */ + + #define NO_OF_BYTES_20MS 38 + #define NO_OF_BYTES_30MS 50 + #define NO_OF_WORDS_20MS 19 + #define NO_OF_WORDS_30MS 25 + #define STATE_BITS 3 + #define BYTE_LEN 8 + #define ULP_CLASSES 3 + + /* help parameters */ + + #define FLOAT_MAX (float)1.0e37 + #define EPS (float)2.220446049250313e-016 + #define PI (float)3.14159265358979323846 + #define MIN_SAMPLE -32768 + #define MAX_SAMPLE 32767 + #define TWO_PI (float)6.283185307 + #define PI2 (float)0.159154943 + + /* type definition encoder instance */ + typedef struct iLBC_ULP_Inst_t_ { + int lsf_bits[6][ULP_CLASSES+2]; + int start_bits[ULP_CLASSES+2]; + int startfirst_bits[ULP_CLASSES+2]; + int scale_bits[ULP_CLASSES+2]; + int state_bits[ULP_CLASSES+2]; + int extra_cb_index[CB_NSTAGES][ULP_CLASSES+2]; + int extra_cb_gain[CB_NSTAGES][ULP_CLASSES+2]; + int cb_index[NSUB_MAX][CB_NSTAGES][ULP_CLASSES+2]; + int cb_gain[NSUB_MAX][CB_NSTAGES][ULP_CLASSES+2]; + } iLBC_ULP_Inst_t; + + /* type definition encoder instance */ + + + +Andersen, et al. Experimental [Page 78] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + typedef struct iLBC_Enc_Inst_t_ { + + /* flag for frame size mode */ + int mode; + + /* basic parameters for different frame sizes */ + int blockl; + int nsub; + int nasub; + int no_of_bytes, no_of_words; + int lpc_n; + int state_short_len; + const iLBC_ULP_Inst_t *ULP_inst; + + /* analysis filter state */ + float anaMem[LPC_FILTERORDER]; + + /* old lsf parameters for interpolation */ + float lsfold[LPC_FILTERORDER]; + float lsfdeqold[LPC_FILTERORDER]; + + /* signal buffer for LP analysis */ + float lpc_buffer[LPC_LOOKBACK + BLOCKL_MAX]; + + /* state of input HP filter */ + float hpimem[4]; + + } iLBC_Enc_Inst_t; + + /* type definition decoder instance */ + typedef struct iLBC_Dec_Inst_t_ { + + /* flag for frame size mode */ + int mode; + + /* basic parameters for different frame sizes */ + int blockl; + int nsub; + int nasub; + int no_of_bytes, no_of_words; + int lpc_n; + int state_short_len; + const iLBC_ULP_Inst_t *ULP_inst; + + /* synthesis filter state */ + float syntMem[LPC_FILTERORDER]; + + /* old LSF for interpolation */ + + + +Andersen, et al. Experimental [Page 79] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + float lsfdeqold[LPC_FILTERORDER]; + + /* pitch lag estimated in enhancer and used in PLC */ + int last_lag; + + /* PLC state information */ + int prevLag, consPLICount, prevPLI, prev_enh_pl; + float prevLpc[LPC_FILTERORDER+1]; + float prevResidual[NSUB_MAX*SUBL]; + float per; + unsigned long seed; + + /* previous synthesis filter parameters */ + float old_syntdenum[(LPC_FILTERORDER + 1)*NSUB_MAX]; + + /* state of output HP filter */ + float hpomem[4]; + + /* enhancer state information */ + int use_enhancer; + float enh_buf[ENH_BUFL]; + float enh_period[ENH_NBLOCKS_TOT]; + + } iLBC_Dec_Inst_t; + + #endif + +A.7. constants.h + + /****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + constants.h + + Copyright (C) The Internet Society (2004). + All Rights Reserved. + + ******************************************************************/ + + #ifndef __iLBC_CONSTANTS_H + #define __iLBC_CONSTANTS_H + + #include "iLBC_define.h" + + + /* ULP bit allocation */ + + + + +Andersen, et al. Experimental [Page 80] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + extern const iLBC_ULP_Inst_t ULP_20msTbl; + extern const iLBC_ULP_Inst_t ULP_30msTbl; + + /* high pass filters */ + + extern float hpi_zero_coefsTbl[]; + extern float hpi_pole_coefsTbl[]; + extern float hpo_zero_coefsTbl[]; + extern float hpo_pole_coefsTbl[]; + + /* low pass filters */ + extern float lpFilt_coefsTbl[]; + + /* LPC analysis and quantization */ + + extern float lpc_winTbl[]; + extern float lpc_asymwinTbl[]; + extern float lpc_lagwinTbl[]; + extern float lsfCbTbl[]; + extern float lsfmeanTbl[]; + extern int dim_lsfCbTbl[]; + extern int size_lsfCbTbl[]; + extern float lsf_weightTbl_30ms[]; + extern float lsf_weightTbl_20ms[]; + + /* state quantization tables */ + + extern float state_sq3Tbl[]; + extern float state_frgqTbl[]; + + /* gain quantization tables */ + + extern float gain_sq3Tbl[]; + extern float gain_sq4Tbl[]; + extern float gain_sq5Tbl[]; + + /* adaptive codebook definitions */ + + extern int search_rangeTbl[5][CB_NSTAGES]; + extern int memLfTbl[]; + extern int stMemLTbl; + extern float cbfiltersTbl[CB_FILTERLEN]; + + /* enhancer definitions */ + + extern float polyphaserTbl[]; + extern float enh_plocsTbl[]; + + + + +Andersen, et al. Experimental [Page 81] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + #endif + +A.8. constants.c + + /****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + constants.c + + Copyright (C) The Internet Society (2004). + All Rights Reserved. + + ******************************************************************/ + + #include "iLBC_define.h" + + /* ULP bit allocation */ + + /* 20 ms frame */ + + const iLBC_ULP_Inst_t ULP_20msTbl = { + /* LSF */ + { {6,0,0,0,0}, {7,0,0,0,0}, {7,0,0,0,0}, + {0,0,0,0,0}, {0,0,0,0,0}, {0,0,0,0,0}}, + /* Start state location, gain and samples */ + {2,0,0,0,0}, + {1,0,0,0,0}, + {6,0,0,0,0}, + {0,1,2,0,0}, + /* extra CB index and extra CB gain */ + {{6,0,1,0,0}, {0,0,7,0,0}, {0,0,7,0,0}}, + {{2,0,3,0,0}, {1,1,2,0,0}, {0,0,3,0,0}}, + /* CB index and CB gain */ + { {{7,0,1,0,0}, {0,0,7,0,0}, {0,0,7,0,0}}, + {{0,0,8,0,0}, {0,0,8,0,0}, {0,0,8,0,0}}, + {{0,0,0,0,0}, {0,0,0,0,0}, {0,0,0,0,0}}, + {{0,0,0,0,0}, {0,0,0,0,0}, {0,0,0,0,0}}}, + { {{1,2,2,0,0}, {1,1,2,0,0}, {0,0,3,0,0}}, + {{1,1,3,0,0}, {0,2,2,0,0}, {0,0,3,0,0}}, + {{0,0,0,0,0}, {0,0,0,0,0}, {0,0,0,0,0}}, + {{0,0,0,0,0}, {0,0,0,0,0}, {0,0,0,0,0}}} + }; + + /* 30 ms frame */ + + const iLBC_ULP_Inst_t ULP_30msTbl = { + /* LSF */ + + + +Andersen, et al. Experimental [Page 82] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + { {6,0,0,0,0}, {7,0,0,0,0}, {7,0,0,0,0}, + {6,0,0,0,0}, {7,0,0,0,0}, {7,0,0,0,0}}, + /* Start state location, gain and samples */ + {3,0,0,0,0}, + {1,0,0,0,0}, + {6,0,0,0,0}, + {0,1,2,0,0}, + /* extra CB index and extra CB gain */ + {{4,2,1,0,0}, {0,0,7,0,0}, {0,0,7,0,0}}, + {{1,1,3,0,0}, {1,1,2,0,0}, {0,0,3,0,0}}, + /* CB index and CB gain */ + { {{6,1,1,0,0}, {0,0,7,0,0}, {0,0,7,0,0}}, + {{0,7,1,0,0}, {0,0,8,0,0}, {0,0,8,0,0}}, + {{0,7,1,0,0}, {0,0,8,0,0}, {0,0,8,0,0}}, + {{0,7,1,0,0}, {0,0,8,0,0}, {0,0,8,0,0}}}, + { {{1,2,2,0,0}, {1,2,1,0,0}, {0,0,3,0,0}}, + {{0,2,3,0,0}, {0,2,2,0,0}, {0,0,3,0,0}}, + {{0,1,4,0,0}, {0,1,3,0,0}, {0,0,3,0,0}}, + {{0,1,4,0,0}, {0,1,3,0,0}, {0,0,3,0,0}}} + }; + + /* HP Filters */ + + float hpi_zero_coefsTbl[3] = { + (float)0.92727436, (float)-1.8544941, (float)0.92727436 + }; + float hpi_pole_coefsTbl[3] = { + (float)1.0, (float)-1.9059465, (float)0.9114024 + }; + float hpo_zero_coefsTbl[3] = { + (float)0.93980581, (float)-1.8795834, (float)0.93980581 + }; + float hpo_pole_coefsTbl[3] = { + (float)1.0, (float)-1.9330735, (float)0.93589199 + }; + + /* LP Filter */ + + float lpFilt_coefsTbl[FILTERORDER_DS]={ + (float)-0.066650, (float)0.125000, (float)0.316650, + (float)0.414063, (float)0.316650, + (float)0.125000, (float)-0.066650 + }; + + /* State quantization tables */ + + float state_sq3Tbl[8] = { + (float)-3.719849, (float)-2.177490, (float)-1.130005, + + + +Andersen, et al. Experimental [Page 83] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + (float)-0.309692, (float)0.444214, (float)1.329712, + (float)2.436279, (float)3.983887 + }; + + float state_frgqTbl[64] = { + (float)1.000085, (float)1.071695, (float)1.140395, + (float)1.206868, (float)1.277188, (float)1.351503, + (float)1.429380, (float)1.500727, (float)1.569049, + (float)1.639599, (float)1.707071, (float)1.781531, + (float)1.840799, (float)1.901550, (float)1.956695, + (float)2.006750, (float)2.055474, (float)2.102787, + (float)2.142819, (float)2.183592, (float)2.217962, + (float)2.257177, (float)2.295739, (float)2.332967, + (float)2.369248, (float)2.402792, (float)2.435080, + (float)2.468598, (float)2.503394, (float)2.539284, + (float)2.572944, (float)2.605036, (float)2.636331, + (float)2.668939, (float)2.698780, (float)2.729101, + (float)2.759786, (float)2.789834, (float)2.818679, + (float)2.848074, (float)2.877470, (float)2.906899, + (float)2.936655, (float)2.967804, (float)3.000115, + (float)3.033367, (float)3.066355, (float)3.104231, + (float)3.141499, (float)3.183012, (float)3.222952, + (float)3.265433, (float)3.308441, (float)3.350823, + (float)3.395275, (float)3.442793, (float)3.490801, + (float)3.542514, (float)3.604064, (float)3.666050, + (float)3.740994, (float)3.830749, (float)3.938770, + (float)4.101764 + }; + + /* CB tables */ + + int search_rangeTbl[5][CB_NSTAGES]={{58,58,58}, {108,44,44}, + {108,108,108}, {108,108,108}, {108,108,108}}; + int stMemLTbl=85; + int memLfTbl[NASUB_MAX]={147,147,147,147}; + + /* expansion filter(s) */ + + float cbfiltersTbl[CB_FILTERLEN]={ + (float)-0.034180, (float)0.108887, (float)-0.184326, + (float)0.806152, (float)0.713379, (float)-0.144043, + (float)0.083740, (float)-0.033691 + }; + + /* Gain Quantization */ + + float gain_sq3Tbl[8]={ + (float)-1.000000, (float)-0.659973, (float)-0.330017, + + + +Andersen, et al. Experimental [Page 84] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + (float)0.000000, (float)0.250000, (float)0.500000, + (float)0.750000, (float)1.00000}; + + float gain_sq4Tbl[16]={ + (float)-1.049988, (float)-0.900024, (float)-0.750000, + (float)-0.599976, (float)-0.450012, (float)-0.299988, + (float)-0.150024, (float)0.000000, (float)0.150024, + (float)0.299988, (float)0.450012, (float)0.599976, + (float)0.750000, (float)0.900024, (float)1.049988, + (float)1.200012}; + + float gain_sq5Tbl[32]={ + (float)0.037476, (float)0.075012, (float)0.112488, + (float)0.150024, (float)0.187500, (float)0.224976, + (float)0.262512, (float)0.299988, (float)0.337524, + (float)0.375000, (float)0.412476, (float)0.450012, + (float)0.487488, (float)0.525024, (float)0.562500, + (float)0.599976, (float)0.637512, (float)0.674988, + (float)0.712524, (float)0.750000, (float)0.787476, + (float)0.825012, (float)0.862488, (float)0.900024, + (float)0.937500, (float)0.974976, (float)1.012512, + (float)1.049988, (float)1.087524, (float)1.125000, + (float)1.162476, (float)1.200012}; + + /* Enhancer - Upsamling a factor 4 (ENH_UPS0 = 4) */ + float polyphaserTbl[ENH_UPS0*(2*ENH_FL0+1)]={ + (float)0.000000, (float)0.000000, (float)0.000000, + (float)1.000000, + (float)0.000000, (float)0.000000, (float)0.000000, + (float)0.015625, (float)-0.076904, (float)0.288330, + (float)0.862061, + (float)-0.106445, (float)0.018799, (float)-0.015625, + (float)0.023682, (float)-0.124268, (float)0.601563, + (float)0.601563, + (float)-0.124268, (float)0.023682, (float)-0.023682, + (float)0.018799, (float)-0.106445, (float)0.862061, + (float)0.288330, + (float)-0.076904, (float)0.015625, (float)-0.018799}; + + float enh_plocsTbl[ENH_NBLOCKS_TOT] = {(float)40.0, (float)120.0, + (float)200.0, (float)280.0, (float)360.0, + (float)440.0, (float)520.0, (float)600.0}; + + /* LPC analysis and quantization */ + + int dim_lsfCbTbl[LSF_NSPLIT] = {3, 3, 4}; + int size_lsfCbTbl[LSF_NSPLIT] = {64,128,128}; + + + + +Andersen, et al. Experimental [Page 85] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + float lsfmeanTbl[LPC_FILTERORDER] = { + (float)0.281738, (float)0.445801, (float)0.663330, + (float)0.962524, (float)1.251831, (float)1.533081, + (float)1.850586, (float)2.137817, (float)2.481445, + (float)2.777344}; + + float lsf_weightTbl_30ms[6] = {(float)(1.0/2.0), (float)1.0, + (float)(2.0/3.0), + (float)(1.0/3.0), (float)0.0, (float)0.0}; + + float lsf_weightTbl_20ms[4] = {(float)(3.0/4.0), (float)(2.0/4.0), + (float)(1.0/4.0), (float)(0.0)}; + + /* Hanning LPC window */ + float lpc_winTbl[BLOCKL_MAX]={ + (float)0.000183, (float)0.000671, (float)0.001526, + (float)0.002716, (float)0.004242, (float)0.006104, + (float)0.008301, (float)0.010834, (float)0.013702, + (float)0.016907, (float)0.020416, (float)0.024261, + (float)0.028442, (float)0.032928, (float)0.037750, + (float)0.042877, (float)0.048309, (float)0.054047, + (float)0.060089, (float)0.066437, (float)0.073090, + (float)0.080017, (float)0.087219, (float)0.094727, + (float)0.102509, (float)0.110535, (float)0.118835, + (float)0.127411, (float)0.136230, (float)0.145294, + (float)0.154602, (float)0.164154, (float)0.173920, + (float)0.183899, (float)0.194122, (float)0.204529, + (float)0.215149, (float)0.225952, (float)0.236938, + (float)0.248108, (float)0.259460, (float)0.270966, + (float)0.282654, (float)0.294464, (float)0.306396, + (float)0.318481, (float)0.330688, (float)0.343018, + (float)0.355438, (float)0.367981, (float)0.380585, + (float)0.393280, (float)0.406067, (float)0.418884, + (float)0.431763, (float)0.444702, (float)0.457672, + (float)0.470673, (float)0.483704, (float)0.496735, + (float)0.509766, (float)0.522797, (float)0.535828, + (float)0.548798, (float)0.561768, (float)0.574677, + (float)0.587524, (float)0.600342, (float)0.613068, + (float)0.625732, (float)0.638306, (float)0.650787, + (float)0.663147, (float)0.675415, (float)0.687561, + (float)0.699585, (float)0.711487, (float)0.723206, + (float)0.734802, (float)0.746216, (float)0.757477, + (float)0.768585, (float)0.779480, (float)0.790192, + (float)0.800720, (float)0.811005, (float)0.821106, + (float)0.830994, (float)0.840668, (float)0.850067, + (float)0.859253, (float)0.868225, (float)0.876892, + (float)0.885345, (float)0.893524, (float)0.901428, + (float)0.909058, (float)0.916412, (float)0.923492, + + + +Andersen, et al. Experimental [Page 86] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + (float)0.930267, (float)0.936768, (float)0.942963, + (float)0.948853, (float)0.954437, (float)0.959717, + (float)0.964691, (float)0.969360, (float)0.973694, + (float)0.977692, (float)0.981384, (float)0.984741, + (float)0.987762, (float)0.990479, (float)0.992828, + (float)0.994873, (float)0.996552, (float)0.997925, + (float)0.998932, (float)0.999603, (float)0.999969, + (float)0.999969, (float)0.999603, (float)0.998932, + (float)0.997925, (float)0.996552, (float)0.994873, + (float)0.992828, (float)0.990479, (float)0.987762, + (float)0.984741, (float)0.981384, (float)0.977692, + (float)0.973694, (float)0.969360, (float)0.964691, + (float)0.959717, (float)0.954437, (float)0.948853, + (float)0.942963, (float)0.936768, (float)0.930267, + (float)0.923492, (float)0.916412, (float)0.909058, + (float)0.901428, (float)0.893524, (float)0.885345, + (float)0.876892, (float)0.868225, (float)0.859253, + (float)0.850067, (float)0.840668, (float)0.830994, + (float)0.821106, (float)0.811005, (float)0.800720, + (float)0.790192, (float)0.779480, (float)0.768585, + (float)0.757477, (float)0.746216, (float)0.734802, + (float)0.723206, (float)0.711487, (float)0.699585, + (float)0.687561, (float)0.675415, (float)0.663147, + (float)0.650787, (float)0.638306, (float)0.625732, + (float)0.613068, (float)0.600342, (float)0.587524, + (float)0.574677, (float)0.561768, (float)0.548798, + (float)0.535828, (float)0.522797, (float)0.509766, + (float)0.496735, (float)0.483704, (float)0.470673, + (float)0.457672, (float)0.444702, (float)0.431763, + (float)0.418884, (float)0.406067, (float)0.393280, + (float)0.380585, (float)0.367981, (float)0.355438, + (float)0.343018, (float)0.330688, (float)0.318481, + (float)0.306396, (float)0.294464, (float)0.282654, + (float)0.270966, (float)0.259460, (float)0.248108, + (float)0.236938, (float)0.225952, (float)0.215149, + (float)0.204529, (float)0.194122, (float)0.183899, + (float)0.173920, (float)0.164154, (float)0.154602, + (float)0.145294, (float)0.136230, (float)0.127411, + (float)0.118835, (float)0.110535, (float)0.102509, + (float)0.094727, (float)0.087219, (float)0.080017, + (float)0.073090, (float)0.066437, (float)0.060089, + (float)0.054047, (float)0.048309, (float)0.042877, + (float)0.037750, (float)0.032928, (float)0.028442, + (float)0.024261, (float)0.020416, (float)0.016907, + (float)0.013702, (float)0.010834, (float)0.008301, + (float)0.006104, (float)0.004242, (float)0.002716, + (float)0.001526, (float)0.000671, (float)0.000183 + }; + + + +Andersen, et al. Experimental [Page 87] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + /* Asymmetric LPC window */ + float lpc_asymwinTbl[BLOCKL_MAX]={ + (float)0.000061, (float)0.000214, (float)0.000458, + (float)0.000824, (float)0.001282, (float)0.001831, + (float)0.002472, (float)0.003235, (float)0.004120, + (float)0.005066, (float)0.006134, (float)0.007294, + (float)0.008545, (float)0.009918, (float)0.011383, + (float)0.012939, (float)0.014587, (float)0.016357, + (float)0.018219, (float)0.020172, (float)0.022217, + (float)0.024353, (float)0.026611, (float)0.028961, + (float)0.031372, (float)0.033905, (float)0.036530, + (float)0.039276, (float)0.042084, (float)0.044983, + (float)0.047974, (float)0.051086, (float)0.054260, + (float)0.057526, (float)0.060883, (float)0.064331, + (float)0.067871, (float)0.071503, (float)0.075226, + (float)0.079010, (float)0.082916, (float)0.086884, + (float)0.090942, (float)0.095062, (float)0.099304, + (float)0.103607, (float)0.107971, (float)0.112427, + (float)0.116974, (float)0.121582, (float)0.126282, + (float)0.131073, (float)0.135895, (float)0.140839, + (float)0.145813, (float)0.150879, (float)0.156006, + (float)0.161224, (float)0.166504, (float)0.171844, + (float)0.177246, (float)0.182709, (float)0.188263, + (float)0.193848, (float)0.199524, (float)0.205231, + (float)0.211029, (float)0.216858, (float)0.222778, + (float)0.228729, (float)0.234741, (float)0.240814, + (float)0.246918, (float)0.253082, (float)0.259308, + (float)0.265564, (float)0.271881, (float)0.278259, + (float)0.284668, (float)0.291107, (float)0.297607, + (float)0.304138, (float)0.310730, (float)0.317322, + (float)0.323975, (float)0.330658, (float)0.337372, + (float)0.344147, (float)0.350922, (float)0.357727, + (float)0.364594, (float)0.371460, (float)0.378357, + (float)0.385284, (float)0.392212, (float)0.399170, + (float)0.406158, (float)0.413177, (float)0.420197, + (float)0.427246, (float)0.434296, (float)0.441376, + (float)0.448456, (float)0.455536, (float)0.462646, + (float)0.469757, (float)0.476868, (float)0.483978, + (float)0.491089, (float)0.498230, (float)0.505341, + (float)0.512451, (float)0.519592, (float)0.526703, + (float)0.533813, (float)0.540924, (float)0.548004, + (float)0.555084, (float)0.562164, (float)0.569244, + (float)0.576294, (float)0.583313, (float)0.590332, + (float)0.597321, (float)0.604309, (float)0.611267, + (float)0.618195, (float)0.625092, (float)0.631989, + (float)0.638855, (float)0.645660, (float)0.652466, + (float)0.659241, (float)0.665985, (float)0.672668, + (float)0.679352, (float)0.685974, (float)0.692566, + + + +Andersen, et al. Experimental [Page 88] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + (float)0.699127, (float)0.705658, (float)0.712128, + (float)0.718536, (float)0.724945, (float)0.731262, + (float)0.737549, (float)0.743805, (float)0.750000, + (float)0.756134, (float)0.762238, (float)0.768280, + (float)0.774261, (float)0.780182, (float)0.786072, + (float)0.791870, (float)0.797638, (float)0.803314, + (float)0.808960, (float)0.814514, (float)0.820038, + (float)0.825470, (float)0.830841, (float)0.836151, + (float)0.841400, (float)0.846558, (float)0.851654, + (float)0.856689, (float)0.861633, (float)0.866516, + (float)0.871338, (float)0.876068, (float)0.880737, + (float)0.885315, (float)0.889801, (float)0.894226, + (float)0.898560, (float)0.902832, (float)0.907013, + (float)0.911102, (float)0.915100, (float)0.919037, + (float)0.922882, (float)0.926636, (float)0.930328, + (float)0.933899, (float)0.937408, (float)0.940796, + (float)0.944122, (float)0.947357, (float)0.950470, + (float)0.953522, (float)0.956482, (float)0.959351, + (float)0.962097, (float)0.964783, (float)0.967377, + (float)0.969849, (float)0.972229, (float)0.974518, + (float)0.976715, (float)0.978821, (float)0.980835, + (float)0.982727, (float)0.984528, (float)0.986237, + (float)0.987854, (float)0.989380, (float)0.990784, + (float)0.992096, (float)0.993317, (float)0.994415, + (float)0.995422, (float)0.996338, (float)0.997162, + (float)0.997864, (float)0.998474, (float)0.998962, + (float)0.999390, (float)0.999695, (float)0.999878, + (float)0.999969, (float)0.999969, (float)0.996918, + (float)0.987701, (float)0.972382, (float)0.951050, + (float)0.923889, (float)0.891022, (float)0.852631, + (float)0.809021, (float)0.760406, (float)0.707092, + (float)0.649445, (float)0.587799, (float)0.522491, + (float)0.453979, (float)0.382690, (float)0.309021, + (float)0.233459, (float)0.156433, (float)0.078461 + }; + + /* Lag window for LPC */ + float lpc_lagwinTbl[LPC_FILTERORDER + 1]={ + (float)1.000100, (float)0.998890, (float)0.995569, + (float)0.990057, (float)0.982392, + (float)0.972623, (float)0.960816, (float)0.947047, + (float)0.931405, (float)0.913989, (float)0.894909}; + + /* LSF quantization*/ + float lsfCbTbl[64 * 3 + 128 * 3 + 128 * 4] = { + (float)0.155396, (float)0.273193, (float)0.451172, + (float)0.390503, (float)0.648071, (float)1.002075, + (float)0.440186, (float)0.692261, (float)0.955688, + + + +Andersen, et al. Experimental [Page 89] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + (float)0.343628, (float)0.642334, (float)1.071533, + (float)0.318359, (float)0.491577, (float)0.670532, + (float)0.193115, (float)0.375488, (float)0.725708, + (float)0.364136, (float)0.510376, (float)0.658691, + (float)0.297485, (float)0.527588, (float)0.842529, + (float)0.227173, (float)0.365967, (float)0.563110, + (float)0.244995, (float)0.396729, (float)0.636475, + (float)0.169434, (float)0.300171, (float)0.520264, + (float)0.312866, (float)0.464478, (float)0.643188, + (float)0.248535, (float)0.429932, (float)0.626099, + (float)0.236206, (float)0.491333, (float)0.817139, + (float)0.334961, (float)0.625122, (float)0.895752, + (float)0.343018, (float)0.518555, (float)0.698608, + (float)0.372803, (float)0.659790, (float)0.945435, + (float)0.176880, (float)0.316528, (float)0.581421, + (float)0.416382, (float)0.625977, (float)0.805176, + (float)0.303223, (float)0.568726, (float)0.915039, + (float)0.203613, (float)0.351440, (float)0.588135, + (float)0.221191, (float)0.375000, (float)0.614746, + (float)0.199951, (float)0.323364, (float)0.476074, + (float)0.300781, (float)0.433350, (float)0.566895, + (float)0.226196, (float)0.354004, (float)0.507568, + (float)0.300049, (float)0.508179, (float)0.711670, + (float)0.312012, (float)0.492676, (float)0.763428, + (float)0.329956, (float)0.541016, (float)0.795776, + (float)0.373779, (float)0.604614, (float)0.928833, + (float)0.210571, (float)0.452026, (float)0.755249, + (float)0.271118, (float)0.473267, (float)0.662476, + (float)0.285522, (float)0.436890, (float)0.634399, + (float)0.246704, (float)0.565552, (float)0.859009, + (float)0.270508, (float)0.406250, (float)0.553589, + (float)0.361450, (float)0.578491, (float)0.813843, + (float)0.342651, (float)0.482788, (float)0.622437, + (float)0.340332, (float)0.549438, (float)0.743164, + (float)0.200439, (float)0.336304, (float)0.540894, + (float)0.407837, (float)0.644775, (float)0.895142, + (float)0.294678, (float)0.454834, (float)0.699097, + (float)0.193115, (float)0.344482, (float)0.643188, + (float)0.275757, (float)0.420776, (float)0.598755, + (float)0.380493, (float)0.608643, (float)0.861084, + (float)0.222778, (float)0.426147, (float)0.676514, + (float)0.407471, (float)0.700195, (float)1.053101, + (float)0.218384, (float)0.377197, (float)0.669922, + (float)0.313232, (float)0.454102, (float)0.600952, + (float)0.347412, (float)0.571533, (float)0.874146, + (float)0.238037, (float)0.405396, (float)0.729492, + (float)0.223877, (float)0.412964, (float)0.822021, + (float)0.395264, (float)0.582153, (float)0.743896, + + + +Andersen, et al. Experimental [Page 90] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + (float)0.247925, (float)0.485596, (float)0.720581, + (float)0.229126, (float)0.496582, (float)0.907715, + (float)0.260132, (float)0.566895, (float)1.012695, + (float)0.337402, (float)0.611572, (float)0.978149, + (float)0.267822, (float)0.447632, (float)0.769287, + (float)0.250610, (float)0.381714, (float)0.530029, + (float)0.430054, (float)0.805054, (float)1.221924, + (float)0.382568, (float)0.544067, (float)0.701660, + (float)0.383545, (float)0.710327, (float)1.149170, + (float)0.271362, (float)0.529053, (float)0.775513, + (float)0.246826, (float)0.393555, (float)0.588623, + (float)0.266846, (float)0.422119, (float)0.676758, + (float)0.311523, (float)0.580688, (float)0.838623, + (float)1.331177, (float)1.576782, (float)1.779541, + (float)1.160034, (float)1.401978, (float)1.768188, + (float)1.161865, (float)1.525146, (float)1.715332, + (float)0.759521, (float)0.913940, (float)1.119873, + (float)0.947144, (float)1.121338, (float)1.282471, + (float)1.015015, (float)1.557007, (float)1.804932, + (float)1.172974, (float)1.402100, (float)1.692627, + (float)1.087524, (float)1.474243, (float)1.665405, + (float)0.899536, (float)1.105225, (float)1.406250, + (float)1.148438, (float)1.484741, (float)1.796265, + (float)0.785645, (float)1.209839, (float)1.567749, + (float)0.867798, (float)1.166504, (float)1.450684, + (float)0.922485, (float)1.229858, (float)1.420898, + (float)0.791260, (float)1.123291, (float)1.409546, + (float)0.788940, (float)0.966064, (float)1.340332, + (float)1.051147, (float)1.272827, (float)1.556641, + (float)0.866821, (float)1.181152, (float)1.538818, + (float)0.906738, (float)1.373535, (float)1.607910, + (float)1.244751, (float)1.581421, (float)1.933838, + (float)0.913940, (float)1.337280, (float)1.539673, + (float)0.680542, (float)0.959229, (float)1.662720, + (float)0.887207, (float)1.430542, (float)1.800781, + (float)0.912598, (float)1.433594, (float)1.683960, + (float)0.860474, (float)1.060303, (float)1.455322, + (float)1.005127, (float)1.381104, (float)1.706909, + (float)0.800781, (float)1.363892, (float)1.829102, + (float)0.781860, (float)1.124390, (float)1.505981, + (float)1.003662, (float)1.471436, (float)1.684692, + (float)0.981323, (float)1.309570, (float)1.618042, + (float)1.228760, (float)1.554321, (float)1.756470, + (float)0.734375, (float)0.895752, (float)1.225586, + (float)0.841797, (float)1.055664, (float)1.249268, + (float)0.920166, (float)1.119385, (float)1.486206, + (float)0.894409, (float)1.539063, (float)1.828979, + (float)1.283691, (float)1.543335, (float)1.858276, + + + +Andersen, et al. 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Experimental [Page 94] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + (float)1.882568, (float)2.332031, (float)2.598267, (float)2.827637, + (float)1.683594, (float)2.088745, (float)2.361938, (float)2.608643, + (float)1.874023, (float)2.182129, (float)2.536133, (float)2.766968, + (float)1.861938, (float)2.070435, (float)2.309692, (float)2.700562, + (float)1.722168, (float)2.107422, (float)2.477295, (float)2.837646, + (float)1.926880, (float)2.184692, (float)2.442627, (float)2.663818, + (float)2.123901, (float)2.337280, (float)2.553101, (float)2.777466, + (float)1.588135, (float)1.911499, (float)2.212769, (float)2.543945, + (float)2.053955, (float)2.370850, (float)2.712158, (float)2.939941, + (float)2.210449, (float)2.519653, (float)2.770386, (float)2.958618, + (float)2.199463, (float)2.474731, (float)2.718262, (float)2.919922, + (float)1.960083, (float)2.175415, (float)2.608032, (float)2.888794, + (float)1.953735, (float)2.185181, (float)2.428223, (float)2.809570, + (float)1.615234, (float)2.036499, (float)2.576538, (float)2.834595, + (float)1.621094, (float)2.028198, (float)2.431030, (float)2.664673, + (float)1.824951, (float)2.267456, (float)2.514526, (float)2.747925, + (float)1.994263, (float)2.229126, (float)2.475220, (float)2.833984, + (float)1.746338, (float)2.011353, (float)2.588257, (float)2.826904, + (float)1.562866, (float)2.135986, (float)2.471680, (float)2.687256, + (float)1.748901, (float)2.083496, (float)2.460938, (float)2.686279, + (float)1.758057, (float)2.131470, (float)2.636597, (float)2.891602, + (float)2.071289, (float)2.299072, (float)2.550781, (float)2.814331, + (float)1.839600, (float)2.094360, (float)2.496460, (float)2.723999, + (float)1.882202, (float)2.088257, (float)2.636841, (float)2.923096, + (float)1.957886, (float)2.153198, (float)2.384399, (float)2.615234, + (float)1.992920, (float)2.351196, (float)2.654419, (float)2.889771, + (float)2.012817, (float)2.262451, (float)2.643799, (float)2.903076, + (float)2.025635, (float)2.254761, (float)2.508423, (float)2.784058, + (float)2.316040, (float)2.589355, (float)2.794189, (float)2.963623, + (float)1.741211, (float)2.279541, (float)2.578491, (float)2.816284, + (float)1.845337, (float)2.055786, (float)2.348511, (float)2.822021, + (float)1.679932, (float)1.926514, (float)2.499756, (float)2.835693, + (float)1.722534, (float)1.946899, (float)2.448486, (float)2.728760, + (float)1.829834, (float)2.043213, (float)2.580444, (float)2.867676, + (float)1.676636, (float)2.071655, (float)2.322510, (float)2.704834, + (float)1.791504, (float)2.113525, (float)2.469727, (float)2.784058, + (float)1.977051, (float)2.215088, (float)2.497437, (float)2.726929, + (float)1.800171, (float)2.106689, (float)2.357788, (float)2.738892, + (float)1.827759, (float)2.170166, (float)2.525879, (float)2.852417, + (float)1.918335, (float)2.132813, (float)2.488403, (float)2.728149, + (float)1.916748, (float)2.225098, (float)2.542603, (float)2.857666, + (float)1.761230, (float)1.976074, (float)2.507446, (float)2.884521, + (float)2.053711, (float)2.367432, (float)2.608032, (float)2.837646, + (float)1.595337, (float)2.000977, (float)2.307129, (float)2.578247, + (float)1.470581, (float)2.031250, (float)2.375854, (float)2.647583, + (float)1.801392, (float)2.128052, (float)2.399780, (float)2.822876, + (float)1.853638, (float)2.066650, (float)2.429199, (float)2.751465, + (float)1.956299, (float)2.163696, (float)2.394775, (float)2.734253, + + + +Andersen, et al. Experimental [Page 95] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + (float)1.963623, (float)2.275757, (float)2.585327, (float)2.865234, + (float)1.887451, (float)2.105469, (float)2.331787, (float)2.587402, + (float)2.120117, (float)2.443359, (float)2.733887, (float)2.941406, + (float)1.506348, (float)1.766968, (float)2.400513, (float)2.851807, + (float)1.664551, (float)1.981079, (float)2.375732, (float)2.774414, + (float)1.720703, (float)1.978882, (float)2.391479, (float)2.640991, + (float)1.483398, (float)1.814819, (float)2.434448, (float)2.722290, + (float)1.769043, (float)2.136597, (float)2.563721, (float)2.774414, + (float)1.810791, (float)2.049316, (float)2.373901, (float)2.613647, + (float)1.788330, (float)2.005981, (float)2.359131, (float)2.723145, + (float)1.785156, (float)1.993164, (float)2.399780, (float)2.832520, + (float)1.695313, (float)2.022949, (float)2.522583, (float)2.745117, + (float)1.584106, (float)1.965576, (float)2.299927, (float)2.715576, + (float)1.894897, (float)2.249878, (float)2.655884, (float)2.897705, + (float)1.720581, (float)1.995728, (float)2.299438, (float)2.557007, + (float)1.619385, (float)2.173950, (float)2.574219, (float)2.787964, + (float)1.883179, (float)2.220459, (float)2.474365, (float)2.825073, + (float)1.447632, (float)2.045044, (float)2.555542, (float)2.744873, + (float)1.502686, (float)2.156616, (float)2.653320, (float)2.846558, + (float)1.711548, (float)1.944092, (float)2.282959, (float)2.685791, + (float)1.499756, (float)1.867554, (float)2.341064, (float)2.578857, + (float)1.916870, (float)2.135132, (float)2.568237, (float)2.826050, + (float)1.498047, (float)1.711182, (float)2.223267, (float)2.755127, + (float)1.808716, (float)1.997559, (float)2.256470, (float)2.758545, + (float)2.088501, (float)2.402710, (float)2.667358, (float)2.890259, + (float)1.545044, (float)1.819214, (float)2.324097, (float)2.692993, + (float)1.796021, (float)2.012573, (float)2.505737, (float)2.784912, + (float)1.786499, (float)2.041748, (float)2.290405, (float)2.650757, + (float)1.938232, (float)2.264404, (float)2.529053, (float)2.796143 + }; + +A.9. anaFilter.h + + /****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + anaFilter.h + + Copyright (C) The Internet Society (2004). + All Rights Reserved. + + ******************************************************************/ + + #ifndef __iLBC_ANAFILTER_H + #define __iLBC_ANAFILTER_H + + void anaFilter( + + + +Andersen, et al. Experimental [Page 96] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + float *In, /* (i) Signal to be filtered */ + float *a, /* (i) LP parameters */ + int len,/* (i) Length of signal */ + float *Out, /* (o) Filtered signal */ + float *mem /* (i/o) Filter state */ + ); + + #endif + +A.10. anaFilter.c + + /****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + anaFilter.c + + Copyright (C) The Internet Society (2004). + All Rights Reserved. + + ******************************************************************/ + + #include <string.h> + #include "iLBC_define.h" + + /*----------------------------------------------------------------* + * LP analysis filter. + *---------------------------------------------------------------*/ + + void anaFilter( + float *In, /* (i) Signal to be filtered */ + float *a, /* (i) LP parameters */ + int len,/* (i) Length of signal */ + float *Out, /* (o) Filtered signal */ + float *mem /* (i/o) Filter state */ + ){ + int i, j; + float *po, *pi, *pm, *pa; + + po = Out; + + /* Filter first part using memory from past */ + + for (i=0; i<LPC_FILTERORDER; i++) { + pi = &In[i]; + pm = &mem[LPC_FILTERORDER-1]; + pa = a; + *po=0.0; + + + +Andersen, et al. Experimental [Page 97] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + for (j=0; j<=i; j++) { + *po+=(*pa++)*(*pi--); + } + for (j=i+1; j<LPC_FILTERORDER+1; j++) { + + *po+=(*pa++)*(*pm--); + } + po++; + } + + /* Filter last part where the state is entirely + in the input vector */ + + for (i=LPC_FILTERORDER; i<len; i++) { + pi = &In[i]; + pa = a; + *po=0.0; + for (j=0; j<LPC_FILTERORDER+1; j++) { + *po+=(*pa++)*(*pi--); + } + po++; + } + + /* Update state vector */ + + memcpy(mem, &In[len-LPC_FILTERORDER], + LPC_FILTERORDER*sizeof(float)); + } + +A.11. createCB.h + + /****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + createCB.h + + Copyright (C) The Internet Society (2004). + All Rights Reserved. + + ******************************************************************/ + + #ifndef __iLBC_CREATECB_H + #define __iLBC_CREATECB_H + + void filteredCBvecs( + float *cbvectors, /* (o) Codebook vector for the + higher section */ + + + +Andersen, et al. Experimental [Page 98] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + float *mem, /* (i) Buffer to create codebook + vectors from */ + int lMem /* (i) Length of buffer */ + ); + + void searchAugmentedCB( + int low, /* (i) Start index for the search */ + int high, /* (i) End index for the search */ + int stage, /* (i) Current stage */ + int startIndex, /* (i) CB index for the first + augmented vector */ + float *target, /* (i) Target vector for encoding */ + float *buffer, /* (i) Pointer to the end of the + buffer for augmented codebook + construction */ + float *max_measure, /* (i/o) Currently maximum measure */ + int *best_index,/* (o) Currently the best index */ + float *gain, /* (o) Currently the best gain */ + float *energy, /* (o) Energy of augmented + codebook vectors */ + float *invenergy/* (o) Inv energy of aug codebook + vectors */ + ); + + void createAugmentedVec( + int index, /* (i) Index for the aug vector + to be created */ + float *buffer, /* (i) Pointer to the end of the + buffer for augmented codebook + construction */ + float *cbVec /* (o) The construced codebook vector */ + ); + + #endif + +A.12. createCB.c + + + /****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + createCB.c + + Copyright (C) The Internet Society (2004). + All Rights Reserved. + + ******************************************************************/ + + + +Andersen, et al. Experimental [Page 99] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + #include "iLBC_define.h" + #include "constants.h" + #include <string.h> + #include <math.h> + + /*----------------------------------------------------------------* + * Construct an additional codebook vector by filtering the + * initial codebook buffer. This vector is then used to expand + * the codebook with an additional section. + *---------------------------------------------------------------*/ + + void filteredCBvecs( + float *cbvectors, /* (o) Codebook vectors for the + higher section */ + float *mem, /* (i) Buffer to create codebook + vector from */ + int lMem /* (i) Length of buffer */ + ){ + int j, k; + float *pp, *pp1; + float tempbuff2[CB_MEML+CB_FILTERLEN]; + float *pos; + + memset(tempbuff2, 0, (CB_HALFFILTERLEN-1)*sizeof(float)); + memcpy(&tempbuff2[CB_HALFFILTERLEN-1], mem, lMem*sizeof(float)); + memset(&tempbuff2[lMem+CB_HALFFILTERLEN-1], 0, + (CB_HALFFILTERLEN+1)*sizeof(float)); + + /* Create codebook vector for higher section by filtering */ + + /* do filtering */ + pos=cbvectors; + memset(pos, 0, lMem*sizeof(float)); + for (k=0; k<lMem; k++) { + pp=&tempbuff2[k]; + pp1=&cbfiltersTbl[CB_FILTERLEN-1]; + for (j=0;j<CB_FILTERLEN;j++) { + (*pos)+=(*pp++)*(*pp1--); + } + pos++; + } + } + + /*----------------------------------------------------------------* + * Search the augmented part of the codebook to find the best + * measure. + *----------------------------------------------------------------*/ + + + + +Andersen, et al. Experimental [Page 100] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + void searchAugmentedCB( + int low, /* (i) Start index for the search */ + int high, /* (i) End index for the search */ + int stage, /* (i) Current stage */ + int startIndex, /* (i) Codebook index for the first + aug vector */ + float *target, /* (i) Target vector for encoding */ + float *buffer, /* (i) Pointer to the end of the buffer for + augmented codebook construction */ + float *max_measure, /* (i/o) Currently maximum measure */ + int *best_index,/* (o) Currently the best index */ + float *gain, /* (o) Currently the best gain */ + float *energy, /* (o) Energy of augmented codebook + vectors */ + float *invenergy/* (o) Inv energy of augmented codebook + vectors */ + ) { + int icount, ilow, j, tmpIndex; + float *pp, *ppo, *ppi, *ppe, crossDot, alfa; + float weighted, measure, nrjRecursive; + float ftmp; + + /* Compute the energy for the first (low-5) + noninterpolated samples */ + nrjRecursive = (float) 0.0; + pp = buffer - low + 1; + for (j=0; j<(low-5); j++) { + nrjRecursive += ( (*pp)*(*pp) ); + pp++; + } + ppe = buffer - low; + + + for (icount=low; icount<=high; icount++) { + + /* Index of the codebook vector used for retrieving + energy values */ + tmpIndex = startIndex+icount-20; + + ilow = icount-4; + + /* Update the energy recursively to save complexity */ + nrjRecursive = nrjRecursive + (*ppe)*(*ppe); + ppe--; + energy[tmpIndex] = nrjRecursive; + + /* Compute cross dot product for the first (low-5) + samples */ + + + +Andersen, et al. Experimental [Page 101] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + crossDot = (float) 0.0; + pp = buffer-icount; + for (j=0; j<ilow; j++) { + crossDot += target[j]*(*pp++); + } + + /* interpolation */ + alfa = (float) 0.2; + ppo = buffer-4; + ppi = buffer-icount-4; + for (j=ilow; j<icount; j++) { + weighted = ((float)1.0-alfa)*(*ppo)+alfa*(*ppi); + ppo++; + ppi++; + energy[tmpIndex] += weighted*weighted; + crossDot += target[j]*weighted; + alfa += (float)0.2; + } + + /* Compute energy and cross dot product for the + remaining samples */ + pp = buffer - icount; + for (j=icount; j<SUBL; j++) { + energy[tmpIndex] += (*pp)*(*pp); + crossDot += target[j]*(*pp++); + } + + if (energy[tmpIndex]>0.0) { + invenergy[tmpIndex]=(float)1.0/(energy[tmpIndex]+EPS); + } else { + invenergy[tmpIndex] = (float) 0.0; + } + + if (stage==0) { + measure = (float)-10000000.0; + + if (crossDot > 0.0) { + measure = crossDot*crossDot*invenergy[tmpIndex]; + } + } + else { + measure = crossDot*crossDot*invenergy[tmpIndex]; + } + + /* check if measure is better */ + ftmp = crossDot*invenergy[tmpIndex]; + + if ((measure>*max_measure) && (fabs(ftmp)<CB_MAXGAIN)) { + + + +Andersen, et al. Experimental [Page 102] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + *best_index = tmpIndex; + *max_measure = measure; + *gain = ftmp; + } + } + } + + + /*----------------------------------------------------------------* + * Recreate a specific codebook vector from the augmented part. + * + *----------------------------------------------------------------*/ + + void createAugmentedVec( + int index, /* (i) Index for the augmented vector + to be created */ + float *buffer, /* (i) Pointer to the end of the buffer for + augmented codebook construction */ + float *cbVec/* (o) The construced codebook vector */ + ) { + int ilow, j; + float *pp, *ppo, *ppi, alfa, alfa1, weighted; + + ilow = index-5; + + /* copy the first noninterpolated part */ + + pp = buffer-index; + memcpy(cbVec,pp,sizeof(float)*index); + + /* interpolation */ + + alfa1 = (float)0.2; + alfa = 0.0; + ppo = buffer-5; + ppi = buffer-index-5; + for (j=ilow; j<index; j++) { + weighted = ((float)1.0-alfa)*(*ppo)+alfa*(*ppi); + ppo++; + ppi++; + cbVec[j] = weighted; + alfa += alfa1; + } + + /* copy the second noninterpolated part */ + + pp = buffer - index; + memcpy(cbVec+index,pp,sizeof(float)*(SUBL-index)); + + + +Andersen, et al. Experimental [Page 103] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + } + +A.13. doCPLC.h + + /****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + doCPLC.h + + Copyright (C) The Internet Society (2004). + All Rights Reserved. + + ******************************************************************/ + + #ifndef __iLBC_DOLPC_H + #define __iLBC_DOLPC_H + + void doThePLC( + float *PLCresidual, /* (o) concealed residual */ + float *PLClpc, /* (o) concealed LP parameters */ + int PLI, /* (i) packet loss indicator + 0 - no PL, 1 = PL */ + float *decresidual, /* (i) decoded residual */ + float *lpc, /* (i) decoded LPC (only used for no PL) */ + int inlag, /* (i) pitch lag */ + iLBC_Dec_Inst_t *iLBCdec_inst + /* (i/o) decoder instance */ + ); + + #endif + +A.14. doCPLC.c + + /****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + doCPLC.c + + Copyright (C) The Internet Society (2004). + All Rights Reserved. + + ******************************************************************/ + + #include <math.h> + #include <string.h> + #include <stdio.h> + + + +Andersen, et al. Experimental [Page 104] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + #include "iLBC_define.h" + + /*----------------------------------------------------------------* + * Compute cross correlation and pitch gain for pitch prediction + * of last subframe at given lag. + *---------------------------------------------------------------*/ + + void compCorr( + float *cc, /* (o) cross correlation coefficient */ + float *gc, /* (o) gain */ + float *pm, + float *buffer, /* (i) signal buffer */ + int lag, /* (i) pitch lag */ + int bLen, /* (i) length of buffer */ + int sRange /* (i) correlation search length */ + ){ + int i; + float ftmp1, ftmp2, ftmp3; + + /* Guard against getting outside buffer */ + if ((bLen-sRange-lag)<0) { + sRange=bLen-lag; + } + + ftmp1 = 0.0; + ftmp2 = 0.0; + ftmp3 = 0.0; + for (i=0; i<sRange; i++) { + ftmp1 += buffer[bLen-sRange+i] * + buffer[bLen-sRange+i-lag]; + ftmp2 += buffer[bLen-sRange+i-lag] * + buffer[bLen-sRange+i-lag]; + ftmp3 += buffer[bLen-sRange+i] * + buffer[bLen-sRange+i]; + } + + if (ftmp2 > 0.0) { + *cc = ftmp1*ftmp1/ftmp2; + *gc = (float)fabs(ftmp1/ftmp2); + *pm=(float)fabs(ftmp1)/ + ((float)sqrt(ftmp2)*(float)sqrt(ftmp3)); + } + else { + *cc = 0.0; + *gc = 0.0; + *pm=0.0; + } + } + + + +Andersen, et al. Experimental [Page 105] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + /*----------------------------------------------------------------* + * Packet loss concealment routine. Conceals a residual signal + * and LP parameters. If no packet loss, update state. + *---------------------------------------------------------------*/ + + void doThePLC( + float *PLCresidual, /* (o) concealed residual */ + float *PLClpc, /* (o) concealed LP parameters */ + int PLI, /* (i) packet loss indicator + 0 - no PL, 1 = PL */ + float *decresidual, /* (i) decoded residual */ + float *lpc, /* (i) decoded LPC (only used for no PL) */ + int inlag, /* (i) pitch lag */ + iLBC_Dec_Inst_t *iLBCdec_inst + /* (i/o) decoder instance */ + ){ + int lag=20, randlag; + float gain, maxcc; + float use_gain; + float gain_comp, maxcc_comp, per, max_per; + int i, pick, use_lag; + float ftmp, randvec[BLOCKL_MAX], pitchfact, energy; + + /* Packet Loss */ + + if (PLI == 1) { + + iLBCdec_inst->consPLICount += 1; + + /* if previous frame not lost, + determine pitch pred. gain */ + + if (iLBCdec_inst->prevPLI != 1) { + + /* Search around the previous lag to find the + best pitch period */ + + lag=inlag-3; + compCorr(&maxcc, &gain, &max_per, + iLBCdec_inst->prevResidual, + lag, iLBCdec_inst->blockl, 60); + for (i=inlag-2;i<=inlag+3;i++) { + compCorr(&maxcc_comp, &gain_comp, &per, + iLBCdec_inst->prevResidual, + i, iLBCdec_inst->blockl, 60); + + if (maxcc_comp>maxcc) { + maxcc=maxcc_comp; + + + +Andersen, et al. Experimental [Page 106] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + gain=gain_comp; + lag=i; + max_per=per; + } + } + + } + + /* previous frame lost, use recorded lag and periodicity */ + + else { + lag=iLBCdec_inst->prevLag; + max_per=iLBCdec_inst->per; + } + + /* downscaling */ + + use_gain=1.0; + if (iLBCdec_inst->consPLICount*iLBCdec_inst->blockl>320) + use_gain=(float)0.9; + else if (iLBCdec_inst->consPLICount* + iLBCdec_inst->blockl>2*320) + use_gain=(float)0.7; + else if (iLBCdec_inst->consPLICount* + iLBCdec_inst->blockl>3*320) + use_gain=(float)0.5; + else if (iLBCdec_inst->consPLICount* + iLBCdec_inst->blockl>4*320) + use_gain=(float)0.0; + + /* mix noise and pitch repeatition */ + ftmp=(float)sqrt(max_per); + if (ftmp>(float)0.7) + pitchfact=(float)1.0; + else if (ftmp>(float)0.4) + pitchfact=(ftmp-(float)0.4)/((float)0.7-(float)0.4); + else + pitchfact=0.0; + + + /* avoid repetition of same pitch cycle */ + use_lag=lag; + if (lag<80) { + use_lag=2*lag; + } + + /* compute concealed residual */ + + + + +Andersen, et al. Experimental [Page 107] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + energy = 0.0; + for (i=0; i<iLBCdec_inst->blockl; i++) { + + /* noise component */ + + iLBCdec_inst->seed=(iLBCdec_inst->seed*69069L+1) & + (0x80000000L-1); + randlag = 50 + ((signed long) iLBCdec_inst->seed)%70; + pick = i - randlag; + + if (pick < 0) { + randvec[i] = + iLBCdec_inst->prevResidual[ + iLBCdec_inst->blockl+pick]; + } else { + randvec[i] = randvec[pick]; + } + + /* pitch repeatition component */ + pick = i - use_lag; + + if (pick < 0) { + PLCresidual[i] = + iLBCdec_inst->prevResidual[ + iLBCdec_inst->blockl+pick]; + } else { + PLCresidual[i] = PLCresidual[pick]; + } + + /* mix random and periodicity component */ + + if (i<80) + PLCresidual[i] = use_gain*(pitchfact * + PLCresidual[i] + + ((float)1.0 - pitchfact) * randvec[i]); + else if (i<160) + PLCresidual[i] = (float)0.95*use_gain*(pitchfact * + PLCresidual[i] + + ((float)1.0 - pitchfact) * randvec[i]); + else + PLCresidual[i] = (float)0.9*use_gain*(pitchfact * + PLCresidual[i] + + ((float)1.0 - pitchfact) * randvec[i]); + + energy += PLCresidual[i] * PLCresidual[i]; + } + + /* less than 30 dB, use only noise */ + + + +Andersen, et al. Experimental [Page 108] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + + if (sqrt(energy/(float)iLBCdec_inst->blockl) < 30.0) { + gain=0.0; + for (i=0; i<iLBCdec_inst->blockl; i++) { + PLCresidual[i] = randvec[i]; + } + } + + /* use old LPC */ + + memcpy(PLClpc,iLBCdec_inst->prevLpc, + (LPC_FILTERORDER+1)*sizeof(float)); + + } + + /* no packet loss, copy input */ + + else { + memcpy(PLCresidual, decresidual, + iLBCdec_inst->blockl*sizeof(float)); + memcpy(PLClpc, lpc, (LPC_FILTERORDER+1)*sizeof(float)); + iLBCdec_inst->consPLICount = 0; + } + + /* update state */ + + if (PLI) { + iLBCdec_inst->prevLag = lag; + iLBCdec_inst->per=max_per; + } + + iLBCdec_inst->prevPLI = PLI; + memcpy(iLBCdec_inst->prevLpc, PLClpc, + (LPC_FILTERORDER+1)*sizeof(float)); + memcpy(iLBCdec_inst->prevResidual, PLCresidual, + iLBCdec_inst->blockl*sizeof(float)); + } + +A.15. enhancer.h + + /****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + enhancer.h + + Copyright (C) The Internet Society (2004). + All Rights Reserved. + + + +Andersen, et al. Experimental [Page 109] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + ******************************************************************/ + + #ifndef __ENHANCER_H + #define __ENHANCER_H + + #include "iLBC_define.h" + + float xCorrCoef( + float *target, /* (i) first array */ + float *regressor, /* (i) second array */ + int subl /* (i) dimension arrays */ + ); + + int enhancerInterface( + float *out, /* (o) the enhanced recidual signal */ + float *in, /* (i) the recidual signal to enhance */ + iLBC_Dec_Inst_t *iLBCdec_inst + /* (i/o) the decoder state structure */ + ); + + #endif + +A.16. enhancer.c + + /****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + enhancer.c + + Copyright (C) The Internet Society (2004). + All Rights Reserved. + + ******************************************************************/ + + #include <math.h> + #include <string.h> + #include "iLBC_define.h" + #include "constants.h" + #include "filter.h" + + /*----------------------------------------------------------------* + * Find index in array such that the array element with said + * index is the element of said array closest to "value" + * according to the squared-error criterion + *---------------------------------------------------------------*/ + + void NearestNeighbor( + + + +Andersen, et al. Experimental [Page 110] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + int *index, /* (o) index of array element closest + to value */ + float *array, /* (i) data array */ + float value,/* (i) value */ + int arlength/* (i) dimension of data array */ + ){ + int i; + float bestcrit,crit; + + crit=array[0]-value; + bestcrit=crit*crit; + *index=0; + for (i=1; i<arlength; i++) { + crit=array[i]-value; + crit=crit*crit; + + if (crit<bestcrit) { + bestcrit=crit; + *index=i; + } + } + } + + /*----------------------------------------------------------------* + * compute cross correlation between sequences + *---------------------------------------------------------------*/ + + void mycorr1( + float* corr, /* (o) correlation of seq1 and seq2 */ + float* seq1, /* (i) first sequence */ + int dim1, /* (i) dimension first seq1 */ + const float *seq2, /* (i) second sequence */ + int dim2 /* (i) dimension seq2 */ + ){ + int i,j; + + for (i=0; i<=dim1-dim2; i++) { + corr[i]=0.0; + for (j=0; j<dim2; j++) { + corr[i] += seq1[i+j] * seq2[j]; + } + } + } + + /*----------------------------------------------------------------* + * upsample finite array assuming zeros outside bounds + *---------------------------------------------------------------*/ + + + + +Andersen, et al. Experimental [Page 111] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + void enh_upsample( + float* useq1, /* (o) upsampled output sequence */ + float* seq1,/* (i) unupsampled sequence */ + int dim1, /* (i) dimension seq1 */ + int hfl /* (i) polyphase filter length=2*hfl+1 */ + ){ + float *pu,*ps; + int i,j,k,q,filterlength,hfl2; + const float *polyp[ENH_UPS0]; /* pointers to + polyphase columns */ + const float *pp; + + /* define pointers for filter */ + + filterlength=2*hfl+1; + + if ( filterlength > dim1 ) { + hfl2=(int) (dim1/2); + for (j=0; j<ENH_UPS0; j++) { + polyp[j]=polyphaserTbl+j*filterlength+hfl-hfl2; + } + hfl=hfl2; + filterlength=2*hfl+1; + } + else { + for (j=0; j<ENH_UPS0; j++) { + polyp[j]=polyphaserTbl+j*filterlength; + } + } + + /* filtering: filter overhangs left side of sequence */ + + pu=useq1; + for (i=hfl; i<filterlength; i++) { + for (j=0; j<ENH_UPS0; j++) { + *pu=0.0; + pp = polyp[j]; + ps = seq1+i; + for (k=0; k<=i; k++) { + *pu += *ps-- * *pp++; + } + pu++; + } + } + + /* filtering: simple convolution=inner products */ + + for (i=filterlength; i<dim1; i++) { + + + +Andersen, et al. Experimental [Page 112] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + for (j=0;j<ENH_UPS0; j++){ + *pu=0.0; + pp = polyp[j]; + ps = seq1+i; + for (k=0; k<filterlength; k++) { + *pu += *ps-- * *pp++; + } + pu++; + } + } + + /* filtering: filter overhangs right side of sequence */ + + for (q=1; q<=hfl; q++) { + for (j=0; j<ENH_UPS0; j++) { + *pu=0.0; + pp = polyp[j]+q; + ps = seq1+dim1-1; + for (k=0; k<filterlength-q; k++) { + *pu += *ps-- * *pp++; + } + pu++; + } + } + } + + + /*----------------------------------------------------------------* + * find segment starting near idata+estSegPos that has highest + * correlation with idata+centerStartPos through + * idata+centerStartPos+ENH_BLOCKL-1 segment is found at a + * resolution of ENH_UPSO times the original of the original + * sampling rate + *---------------------------------------------------------------*/ + + void refiner( + float *seg, /* (o) segment array */ + float *updStartPos, /* (o) updated start point */ + float* idata, /* (i) original data buffer */ + int idatal, /* (i) dimension of idata */ + int centerStartPos, /* (i) beginning center segment */ + float estSegPos,/* (i) estimated beginning other segment */ + float period /* (i) estimated pitch period */ + ){ + int estSegPosRounded,searchSegStartPos,searchSegEndPos,corrdim; + int tloc,tloc2,i,st,en,fraction; + float vect[ENH_VECTL],corrVec[ENH_CORRDIM],maxv; + float corrVecUps[ENH_CORRDIM*ENH_UPS0]; + + + +Andersen, et al. Experimental [Page 113] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + /* defining array bounds */ + + estSegPosRounded=(int)(estSegPos - 0.5); + + searchSegStartPos=estSegPosRounded-ENH_SLOP; + + if (searchSegStartPos<0) { + searchSegStartPos=0; + } + searchSegEndPos=estSegPosRounded+ENH_SLOP; + + if (searchSegEndPos+ENH_BLOCKL >= idatal) { + searchSegEndPos=idatal-ENH_BLOCKL-1; + } + corrdim=searchSegEndPos-searchSegStartPos+1; + + /* compute upsampled correlation (corr33) and find + location of max */ + + mycorr1(corrVec,idata+searchSegStartPos, + corrdim+ENH_BLOCKL-1,idata+centerStartPos,ENH_BLOCKL); + enh_upsample(corrVecUps,corrVec,corrdim,ENH_FL0); + tloc=0; maxv=corrVecUps[0]; + for (i=1; i<ENH_UPS0*corrdim; i++) { + + if (corrVecUps[i]>maxv) { + tloc=i; + maxv=corrVecUps[i]; + } + } + + /* make vector can be upsampled without ever running outside + bounds */ + + *updStartPos= (float)searchSegStartPos + + (float)tloc/(float)ENH_UPS0+(float)1.0; + tloc2=(int)(tloc/ENH_UPS0); + + if (tloc>tloc2*ENH_UPS0) { + tloc2++; + } + st=searchSegStartPos+tloc2-ENH_FL0; + + if (st<0) { + memset(vect,0,-st*sizeof(float)); + memcpy(&vect[-st],idata, (ENH_VECTL+st)*sizeof(float)); + } + else { + + + +Andersen, et al. Experimental [Page 114] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + en=st+ENH_VECTL; + + if (en>idatal) { + memcpy(vect, &idata[st], + (ENH_VECTL-(en-idatal))*sizeof(float)); + memset(&vect[ENH_VECTL-(en-idatal)], 0, + (en-idatal)*sizeof(float)); + } + else { + memcpy(vect, &idata[st], ENH_VECTL*sizeof(float)); + } + } + fraction=tloc2*ENH_UPS0-tloc; + + /* compute the segment (this is actually a convolution) */ + + mycorr1(seg,vect,ENH_VECTL,polyphaserTbl+(2*ENH_FL0+1)*fraction, + 2*ENH_FL0+1); + } + + /*----------------------------------------------------------------* + * find the smoothed output data + *---------------------------------------------------------------*/ + + void smath( + float *odata, /* (o) smoothed output */ + float *sseq,/* (i) said second sequence of waveforms */ + int hl, /* (i) 2*hl+1 is sseq dimension */ + float alpha0/* (i) max smoothing energy fraction */ + ){ + int i,k; + float w00,w10,w11,A,B,C,*psseq,err,errs; + float surround[BLOCKL_MAX]; /* shape contributed by other than + current */ + float wt[2*ENH_HL+1]; /* waveform weighting to get + surround shape */ + float denom; + + /* create shape of contribution from all waveforms except the + current one */ + + for (i=1; i<=2*hl+1; i++) { + wt[i-1] = (float)0.5*(1 - (float)cos(2*PI*i/(2*hl+2))); + } + wt[hl]=0.0; /* for clarity, not used */ + for (i=0; i<ENH_BLOCKL; i++) { + surround[i]=sseq[i]*wt[0]; + } + + + +Andersen, et al. Experimental [Page 115] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + for (k=1; k<hl; k++) { + psseq=sseq+k*ENH_BLOCKL; + for(i=0;i<ENH_BLOCKL; i++) { + surround[i]+=psseq[i]*wt[k]; + } + } + for (k=hl+1; k<=2*hl; k++) { + psseq=sseq+k*ENH_BLOCKL; + for(i=0;i<ENH_BLOCKL; i++) { + surround[i]+=psseq[i]*wt[k]; + } + } + + /* compute some inner products */ + + w00 = w10 = w11 = 0.0; + psseq=sseq+hl*ENH_BLOCKL; /* current block */ + for (i=0; i<ENH_BLOCKL;i++) { + w00+=psseq[i]*psseq[i]; + w11+=surround[i]*surround[i]; + w10+=surround[i]*psseq[i]; + } + + if (fabs(w11) < 1.0) { + w11=1.0; + } + C = (float)sqrt( w00/w11); + + /* first try enhancement without power-constraint */ + + errs=0.0; + psseq=sseq+hl*ENH_BLOCKL; + for (i=0; i<ENH_BLOCKL; i++) { + odata[i]=C*surround[i]; + err=psseq[i]-odata[i]; + errs+=err*err; + } + + /* if constraint violated by first try, add constraint */ + + if (errs > alpha0 * w00) { + if ( w00 < 1) { + w00=1; + } + denom = (w11*w00-w10*w10)/(w00*w00); + + if (denom > 0.0001) { /* eliminates numerical problems + for if smooth */ + + + +Andersen, et al. Experimental [Page 116] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + A = (float)sqrt( (alpha0- alpha0*alpha0/4)/denom); + B = -alpha0/2 - A * w10/w00; + B = B+1; + } + else { /* essentially no difference between cycles; + smoothing not needed */ + A= 0.0; + B= 1.0; + } + + /* create smoothed sequence */ + + psseq=sseq+hl*ENH_BLOCKL; + for (i=0; i<ENH_BLOCKL; i++) { + odata[i]=A*surround[i]+B*psseq[i]; + } + } + } + + /*----------------------------------------------------------------* + * get the pitch-synchronous sample sequence + *---------------------------------------------------------------*/ + + void getsseq( + float *sseq, /* (o) the pitch-synchronous sequence */ + float *idata, /* (i) original data */ + int idatal, /* (i) dimension of data */ + int centerStartPos, /* (i) where current block starts */ + float *period, /* (i) rough-pitch-period array */ + float *plocs, /* (i) where periods of period array + are taken */ + int periodl, /* (i) dimension period array */ + int hl /* (i) 2*hl+1 is the number of sequences */ + ){ + int i,centerEndPos,q; + float blockStartPos[2*ENH_HL+1]; + int lagBlock[2*ENH_HL+1]; + float plocs2[ENH_PLOCSL]; + float *psseq; + + centerEndPos=centerStartPos+ENH_BLOCKL-1; + + /* present */ + + NearestNeighbor(lagBlock+hl,plocs, + (float)0.5*(centerStartPos+centerEndPos),periodl); + + blockStartPos[hl]=(float)centerStartPos; + + + +Andersen, et al. Experimental [Page 117] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + psseq=sseq+ENH_BLOCKL*hl; + memcpy(psseq, idata+centerStartPos, ENH_BLOCKL*sizeof(float)); + + /* past */ + + for (q=hl-1; q>=0; q--) { + blockStartPos[q]=blockStartPos[q+1]-period[lagBlock[q+1]]; + NearestNeighbor(lagBlock+q,plocs, + blockStartPos[q]+ + ENH_BLOCKL_HALF-period[lagBlock[q+1]], periodl); + + + if (blockStartPos[q]-ENH_OVERHANG>=0) { + refiner(sseq+q*ENH_BLOCKL, blockStartPos+q, idata, + idatal, centerStartPos, blockStartPos[q], + period[lagBlock[q+1]]); + } else { + psseq=sseq+q*ENH_BLOCKL; + memset(psseq, 0, ENH_BLOCKL*sizeof(float)); + } + } + + /* future */ + + for (i=0; i<periodl; i++) { + plocs2[i]=plocs[i]-period[i]; + } + for (q=hl+1; q<=2*hl; q++) { + NearestNeighbor(lagBlock+q,plocs2, + blockStartPos[q-1]+ENH_BLOCKL_HALF,periodl); + + blockStartPos[q]=blockStartPos[q-1]+period[lagBlock[q]]; + if (blockStartPos[q]+ENH_BLOCKL+ENH_OVERHANG<idatal) { + refiner(sseq+ENH_BLOCKL*q, blockStartPos+q, idata, + idatal, centerStartPos, blockStartPos[q], + period[lagBlock[q]]); + } + else { + psseq=sseq+q*ENH_BLOCKL; + memset(psseq, 0, ENH_BLOCKL*sizeof(float)); + } + } + } + + /*----------------------------------------------------------------* + * perform enhancement on idata+centerStartPos through + * idata+centerStartPos+ENH_BLOCKL-1 + *---------------------------------------------------------------*/ + + + +Andersen, et al. Experimental [Page 118] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + void enhancer( + float *odata, /* (o) smoothed block, dimension blockl */ + float *idata, /* (i) data buffer used for enhancing */ + int idatal, /* (i) dimension idata */ + int centerStartPos, /* (i) first sample current block + within idata */ + float alpha0, /* (i) max correction-energy-fraction + (in [0,1]) */ + float *period, /* (i) pitch period array */ + float *plocs, /* (i) locations where period array + values valid */ + int periodl /* (i) dimension of period and plocs */ + ){ + float sseq[(2*ENH_HL+1)*ENH_BLOCKL]; + + /* get said second sequence of segments */ + + getsseq(sseq,idata,idatal,centerStartPos,period, + plocs,periodl,ENH_HL); + + /* compute the smoothed output from said second sequence */ + + smath(odata,sseq,ENH_HL,alpha0); + + } + + /*----------------------------------------------------------------* + * cross correlation + *---------------------------------------------------------------*/ + + float xCorrCoef( + float *target, /* (i) first array */ + float *regressor, /* (i) second array */ + int subl /* (i) dimension arrays */ + ){ + int i; + float ftmp1, ftmp2; + + ftmp1 = 0.0; + ftmp2 = 0.0; + for (i=0; i<subl; i++) { + ftmp1 += target[i]*regressor[i]; + ftmp2 += regressor[i]*regressor[i]; + } + + if (ftmp1 > 0.0) { + return (float)(ftmp1*ftmp1/ftmp2); + } + + + +Andersen, et al. Experimental [Page 119] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + else { + return (float)0.0; + } + } + + /*----------------------------------------------------------------* + * interface for enhancer + *---------------------------------------------------------------*/ + + int enhancerInterface( + float *out, /* (o) enhanced signal */ + float *in, /* (i) unenhanced signal */ + iLBC_Dec_Inst_t *iLBCdec_inst /* (i) buffers etc */ + ){ + float *enh_buf, *enh_period; + int iblock, isample; + int lag=0, ilag, i, ioffset; + float cc, maxcc; + float ftmp1, ftmp2; + float *inPtr, *enh_bufPtr1, *enh_bufPtr2; + float plc_pred[ENH_BLOCKL]; + + float lpState[6], downsampled[(ENH_NBLOCKS*ENH_BLOCKL+120)/2]; + int inLen=ENH_NBLOCKS*ENH_BLOCKL+120; + int start, plc_blockl, inlag; + + enh_buf=iLBCdec_inst->enh_buf; + enh_period=iLBCdec_inst->enh_period; + + memmove(enh_buf, &enh_buf[iLBCdec_inst->blockl], + (ENH_BUFL-iLBCdec_inst->blockl)*sizeof(float)); + + memcpy(&enh_buf[ENH_BUFL-iLBCdec_inst->blockl], in, + iLBCdec_inst->blockl*sizeof(float)); + + if (iLBCdec_inst->mode==30) + plc_blockl=ENH_BLOCKL; + else + plc_blockl=40; + + /* when 20 ms frame, move processing one block */ + ioffset=0; + if (iLBCdec_inst->mode==20) ioffset=1; + + i=3-ioffset; + memmove(enh_period, &enh_period[i], + (ENH_NBLOCKS_TOT-i)*sizeof(float)); + + + + +Andersen, et al. Experimental [Page 120] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + /* Set state information to the 6 samples right before + the samples to be downsampled. */ + + memcpy(lpState, + enh_buf+(ENH_NBLOCKS_EXTRA+ioffset)*ENH_BLOCKL-126, + 6*sizeof(float)); + + /* Down sample a factor 2 to save computations */ + + DownSample(enh_buf+(ENH_NBLOCKS_EXTRA+ioffset)*ENH_BLOCKL-120, + lpFilt_coefsTbl, inLen-ioffset*ENH_BLOCKL, + lpState, downsampled); + + /* Estimate the pitch in the down sampled domain. */ + for (iblock = 0; iblock<ENH_NBLOCKS-ioffset; iblock++) { + + lag = 10; + maxcc = xCorrCoef(downsampled+60+iblock* + ENH_BLOCKL_HALF, downsampled+60+iblock* + ENH_BLOCKL_HALF-lag, ENH_BLOCKL_HALF); + for (ilag=11; ilag<60; ilag++) { + cc = xCorrCoef(downsampled+60+iblock* + ENH_BLOCKL_HALF, downsampled+60+iblock* + ENH_BLOCKL_HALF-ilag, ENH_BLOCKL_HALF); + + if (cc > maxcc) { + maxcc = cc; + lag = ilag; + } + } + + /* Store the estimated lag in the non-downsampled domain */ + enh_period[iblock+ENH_NBLOCKS_EXTRA+ioffset] = (float)lag*2; + + + } + + + /* PLC was performed on the previous packet */ + if (iLBCdec_inst->prev_enh_pl==1) { + + inlag=(int)enh_period[ENH_NBLOCKS_EXTRA+ioffset]; + + lag = inlag-1; + maxcc = xCorrCoef(in, in+lag, plc_blockl); + for (ilag=inlag; ilag<=inlag+1; ilag++) { + cc = xCorrCoef(in, in+ilag, plc_blockl); + + + + +Andersen, et al. Experimental [Page 121] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + if (cc > maxcc) { + maxcc = cc; + lag = ilag; + } + } + + enh_period[ENH_NBLOCKS_EXTRA+ioffset-1]=(float)lag; + + /* compute new concealed residual for the old lookahead, + mix the forward PLC with a backward PLC from + the new frame */ + + inPtr=&in[lag-1]; + + enh_bufPtr1=&plc_pred[plc_blockl-1]; + + if (lag>plc_blockl) { + start=plc_blockl; + } else { + start=lag; + } + + for (isample = start; isample>0; isample--) { + *enh_bufPtr1-- = *inPtr--; + } + + enh_bufPtr2=&enh_buf[ENH_BUFL-1-iLBCdec_inst->blockl]; + for (isample = (plc_blockl-1-lag); isample>=0; isample--) { + *enh_bufPtr1-- = *enh_bufPtr2--; + } + + /* limit energy change */ + ftmp2=0.0; + ftmp1=0.0; + for (i=0;i<plc_blockl;i++) { + ftmp2+=enh_buf[ENH_BUFL-1-iLBCdec_inst->blockl-i]* + enh_buf[ENH_BUFL-1-iLBCdec_inst->blockl-i]; + ftmp1+=plc_pred[i]*plc_pred[i]; + } + ftmp1=(float)sqrt(ftmp1/(float)plc_blockl); + ftmp2=(float)sqrt(ftmp2/(float)plc_blockl); + if (ftmp1>(float)2.0*ftmp2 && ftmp1>0.0) { + for (i=0;i<plc_blockl-10;i++) { + plc_pred[i]*=(float)2.0*ftmp2/ftmp1; + } + for (i=plc_blockl-10;i<plc_blockl;i++) { + plc_pred[i]*=(float)(i-plc_blockl+10)* + ((float)1.0-(float)2.0*ftmp2/ftmp1)/(float)(10)+ + + + +Andersen, et al. Experimental [Page 122] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + (float)2.0*ftmp2/ftmp1; + } + } + + enh_bufPtr1=&enh_buf[ENH_BUFL-1-iLBCdec_inst->blockl]; + for (i=0; i<plc_blockl; i++) { + ftmp1 = (float) (i+1) / (float) (plc_blockl+1); + *enh_bufPtr1 *= ftmp1; + *enh_bufPtr1 += ((float)1.0-ftmp1)* + plc_pred[plc_blockl-1-i]; + enh_bufPtr1--; + } + } + + if (iLBCdec_inst->mode==20) { + /* Enhancer with 40 samples delay */ + for (iblock = 0; iblock<2; iblock++) { + enhancer(out+iblock*ENH_BLOCKL, enh_buf, + ENH_BUFL, (5+iblock)*ENH_BLOCKL+40, + ENH_ALPHA0, enh_period, enh_plocsTbl, + ENH_NBLOCKS_TOT); + } + } else if (iLBCdec_inst->mode==30) { + /* Enhancer with 80 samples delay */ + for (iblock = 0; iblock<3; iblock++) { + enhancer(out+iblock*ENH_BLOCKL, enh_buf, + ENH_BUFL, (4+iblock)*ENH_BLOCKL, + ENH_ALPHA0, enh_period, enh_plocsTbl, + ENH_NBLOCKS_TOT); + } + } + + return (lag*2); + } + +A.17. filter.h + + /****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + filter.h + + Copyright (C) The Internet Society (2004). + All Rights Reserved. + + ******************************************************************/ + + + + +Andersen, et al. Experimental [Page 123] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + #ifndef __iLBC_FILTER_H + #define __iLBC_FILTER_H + + void AllPoleFilter( + float *InOut, /* (i/o) on entrance InOut[-orderCoef] to + InOut[-1] contain the state of the + filter (delayed samples). InOut[0] to + InOut[lengthInOut-1] contain the filter + input, on en exit InOut[-orderCoef] to + InOut[-1] is unchanged and InOut[0] to + InOut[lengthInOut-1] contain filtered + samples */ + float *Coef,/* (i) filter coefficients, Coef[0] is assumed + to be 1.0 */ + int lengthInOut,/* (i) number of input/output samples */ + int orderCoef /* (i) number of filter coefficients */ + ); + + void AllZeroFilter( + float *In, /* (i) In[0] to In[lengthInOut-1] contain + filter input samples */ + float *Coef,/* (i) filter coefficients (Coef[0] is assumed + to be 1.0) */ + int lengthInOut,/* (i) number of input/output samples */ + int orderCoef, /* (i) number of filter coefficients */ + float *Out /* (i/o) on entrance Out[-orderCoef] to Out[-1] + contain the filter state, on exit Out[0] + to Out[lengthInOut-1] contain filtered + samples */ + ); + + void ZeroPoleFilter( + float *In, /* (i) In[0] to In[lengthInOut-1] contain filter + input samples In[-orderCoef] to In[-1] + contain state of all-zero section */ + float *ZeroCoef,/* (i) filter coefficients for all-zero + section (ZeroCoef[0] is assumed to + be 1.0) */ + float *PoleCoef,/* (i) filter coefficients for all-pole section + (ZeroCoef[0] is assumed to be 1.0) */ + int lengthInOut,/* (i) number of input/output samples */ + int orderCoef, /* (i) number of filter coefficients */ + float *Out /* (i/o) on entrance Out[-orderCoef] to Out[-1] + contain state of all-pole section. On + exit Out[0] to Out[lengthInOut-1] + contain filtered samples */ + ); + + + + +Andersen, et al. Experimental [Page 124] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + void DownSample ( + float *In, /* (i) input samples */ + float *Coef, /* (i) filter coefficients */ + int lengthIn, /* (i) number of input samples */ + float *state, /* (i) filter state */ + float *Out /* (o) downsampled output */ + ); + + #endif + +A.18. filter.c + + /****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + filter.c + + Copyright (C) The Internet Society (2004). + All Rights Reserved. + + ******************************************************************/ + + #include "iLBC_define.h" + + /*----------------------------------------------------------------* + * all-pole filter + *---------------------------------------------------------------*/ + + void AllPoleFilter( + float *InOut, /* (i/o) on entrance InOut[-orderCoef] to + InOut[-1] contain the state of the + filter (delayed samples). InOut[0] to + InOut[lengthInOut-1] contain the filter + input, on en exit InOut[-orderCoef] to + InOut[-1] is unchanged and InOut[0] to + InOut[lengthInOut-1] contain filtered + samples */ + float *Coef,/* (i) filter coefficients, Coef[0] is assumed + to be 1.0 */ + int lengthInOut,/* (i) number of input/output samples */ + int orderCoef /* (i) number of filter coefficients */ + ){ + int n,k; + + for(n=0;n<lengthInOut;n++){ + for(k=1;k<=orderCoef;k++){ + *InOut -= Coef[k]*InOut[-k]; + + + +Andersen, et al. Experimental [Page 125] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + } + InOut++; + } + } + + /*----------------------------------------------------------------* + * all-zero filter + *---------------------------------------------------------------*/ + + void AllZeroFilter( + float *In, /* (i) In[0] to In[lengthInOut-1] contain + filter input samples */ + float *Coef,/* (i) filter coefficients (Coef[0] is assumed + to be 1.0) */ + int lengthInOut,/* (i) number of input/output samples */ + int orderCoef, /* (i) number of filter coefficients */ + float *Out /* (i/o) on entrance Out[-orderCoef] to Out[-1] + contain the filter state, on exit Out[0] + to Out[lengthInOut-1] contain filtered + samples */ + ){ + int n,k; + + for(n=0;n<lengthInOut;n++){ + *Out = Coef[0]*In[0]; + for(k=1;k<=orderCoef;k++){ + *Out += Coef[k]*In[-k]; + } + Out++; + In++; + } + } + + /*----------------------------------------------------------------* + * pole-zero filter + *---------------------------------------------------------------*/ + + void ZeroPoleFilter( + float *In, /* (i) In[0] to In[lengthInOut-1] contain + filter input samples In[-orderCoef] to + In[-1] contain state of all-zero + section */ + float *ZeroCoef,/* (i) filter coefficients for all-zero + section (ZeroCoef[0] is assumed to + be 1.0) */ + float *PoleCoef,/* (i) filter coefficients for all-pole section + (ZeroCoef[0] is assumed to be 1.0) */ + int lengthInOut,/* (i) number of input/output samples */ + + + +Andersen, et al. Experimental [Page 126] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + int orderCoef, /* (i) number of filter coefficients */ + float *Out /* (i/o) on entrance Out[-orderCoef] to Out[-1] + contain state of all-pole section. On + exit Out[0] to Out[lengthInOut-1] + contain filtered samples */ + ){ + AllZeroFilter(In,ZeroCoef,lengthInOut,orderCoef,Out); + AllPoleFilter(Out,PoleCoef,lengthInOut,orderCoef); + } + + /*----------------------------------------------------------------* + * downsample (LP filter and decimation) + *---------------------------------------------------------------*/ + + void DownSample ( + float *In, /* (i) input samples */ + float *Coef, /* (i) filter coefficients */ + int lengthIn, /* (i) number of input samples */ + float *state, /* (i) filter state */ + float *Out /* (o) downsampled output */ + ){ + float o; + float *Out_ptr = Out; + float *Coef_ptr, *In_ptr; + float *state_ptr; + int i, j, stop; + + /* LP filter and decimate at the same time */ + + for (i = DELAY_DS; i < lengthIn; i+=FACTOR_DS) + { + Coef_ptr = &Coef[0]; + In_ptr = &In[i]; + state_ptr = &state[FILTERORDER_DS-2]; + + o = (float)0.0; + + stop = (i < FILTERORDER_DS) ? i + 1 : FILTERORDER_DS; + + for (j = 0; j < stop; j++) + { + o += *Coef_ptr++ * (*In_ptr--); + } + for (j = i + 1; j < FILTERORDER_DS; j++) + { + o += *Coef_ptr++ * (*state_ptr--); + } + + + + +Andersen, et al. Experimental [Page 127] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + *Out_ptr++ = o; + } + + /* Get the last part (use zeros as input for the future) */ + + for (i=(lengthIn+FACTOR_DS); i<(lengthIn+DELAY_DS); + i+=FACTOR_DS) { + + o=(float)0.0; + + if (i<lengthIn) { + Coef_ptr = &Coef[0]; + In_ptr = &In[i]; + for (j=0; j<FILTERORDER_DS; j++) { + o += *Coef_ptr++ * (*Out_ptr--); + } + } else { + Coef_ptr = &Coef[i-lengthIn]; + In_ptr = &In[lengthIn-1]; + for (j=0; j<FILTERORDER_DS-(i-lengthIn); j++) { + o += *Coef_ptr++ * (*In_ptr--); + } + } + *Out_ptr++ = o; + } + } + +A.19. FrameClassify.h + + /****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + FrameClassify.h + + Copyright (C) The Internet Society (2004). + All Rights Reserved. + + ******************************************************************/ + + #ifndef __iLBC_FRAMECLASSIFY_H + #define __iLBC_FRAMECLASSIFY_H + + int FrameClassify( /* index to the max-energy sub-frame */ + iLBC_Enc_Inst_t *iLBCenc_inst, + /* (i/o) the encoder state structure */ + float *residual /* (i) lpc residual signal */ + ); + + + +Andersen, et al. Experimental [Page 128] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + #endif + +A.20. FrameClassify.c + + /****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + FrameClassify.c + + Copyright (C) The Internet Society (2004). + All Rights Reserved. + + ******************************************************************/ + + #include "iLBC_define.h" + + /*---------------------------------------------------------------* + * Classification of subframes to localize start state + *--------------------------------------------------------------*/ + + int FrameClassify( /* index to the max-energy sub-frame */ + iLBC_Enc_Inst_t *iLBCenc_inst, + /* (i/o) the encoder state structure */ + float *residual /* (i) lpc residual signal */ + ) { + float max_ssqEn, fssqEn[NSUB_MAX], bssqEn[NSUB_MAX], *pp; + int n, l, max_ssqEn_n; + const float ssqEn_win[NSUB_MAX-1]={(float)0.8,(float)0.9, + (float)1.0,(float)0.9,(float)0.8}; + const float sampEn_win[5]={(float)1.0/(float)6.0, + (float)2.0/(float)6.0, (float)3.0/(float)6.0, + (float)4.0/(float)6.0, (float)5.0/(float)6.0}; + + /* init the front and back energies to zero */ + + memset(fssqEn, 0, NSUB_MAX*sizeof(float)); + memset(bssqEn, 0, NSUB_MAX*sizeof(float)); + + /* Calculate front of first seqence */ + + n=0; + pp=residual; + for (l=0; l<5; l++) { + fssqEn[n] += sampEn_win[l] * (*pp) * (*pp); + pp++; + } + for (l=5; l<SUBL; l++) { + + + +Andersen, et al. Experimental [Page 129] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + fssqEn[n] += (*pp) * (*pp); + pp++; + } + + /* Calculate front and back of all middle sequences */ + + for (n=1; n<iLBCenc_inst->nsub-1; n++) { + pp=residual+n*SUBL; + for (l=0; l<5; l++) { + fssqEn[n] += sampEn_win[l] * (*pp) * (*pp); + bssqEn[n] += (*pp) * (*pp); + pp++; + } + for (l=5; l<SUBL-5; l++) { + fssqEn[n] += (*pp) * (*pp); + bssqEn[n] += (*pp) * (*pp); + pp++; + } + for (l=SUBL-5; l<SUBL; l++) { + fssqEn[n] += (*pp) * (*pp); + bssqEn[n] += sampEn_win[SUBL-l-1] * (*pp) * (*pp); + pp++; + } + } + + /* Calculate back of last seqence */ + + n=iLBCenc_inst->nsub-1; + pp=residual+n*SUBL; + for (l=0; l<SUBL-5; l++) { + bssqEn[n] += (*pp) * (*pp); + pp++; + } + for (l=SUBL-5; l<SUBL; l++) { + bssqEn[n] += sampEn_win[SUBL-l-1] * (*pp) * (*pp); + pp++; + } + + /* find the index to the weighted 80 sample with + most energy */ + + if (iLBCenc_inst->mode==20) l=1; + else l=0; + + max_ssqEn=(fssqEn[0]+bssqEn[1])*ssqEn_win[l]; + max_ssqEn_n=1; + for (n=2; n<iLBCenc_inst->nsub; n++) { + + + + +Andersen, et al. Experimental [Page 130] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + l++; + if ((fssqEn[n-1]+bssqEn[n])*ssqEn_win[l] > max_ssqEn) { + max_ssqEn=(fssqEn[n-1]+bssqEn[n]) * + ssqEn_win[l]; + max_ssqEn_n=n; + } + } + + return max_ssqEn_n; + } + +A.21. gainquant.h + + /****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + gainquant.h + + Copyright (C) The Internet Society (2004). + All Rights Reserved. + + ******************************************************************/ + + #ifndef __iLBC_GAINQUANT_H + #define __iLBC_GAINQUANT_H + + float gainquant(/* (o) quantized gain value */ + float in, /* (i) gain value */ + float maxIn,/* (i) maximum of gain value */ + int cblen, /* (i) number of quantization indices */ + int *index /* (o) quantization index */ + ); + + float gaindequant( /* (o) quantized gain value */ + int index, /* (i) quantization index */ + float maxIn,/* (i) maximum of unquantized gain */ + int cblen /* (i) number of quantization indices */ + ); + + #endif + +A.22. gainquant.c + + /****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + + + +Andersen, et al. Experimental [Page 131] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + gainquant.c + + Copyright (C) The Internet Society (2004). + All Rights Reserved. + + ******************************************************************/ + + #include <string.h> + #include <math.h> + #include "constants.h" + #include "filter.h" + + /*----------------------------------------------------------------* + * quantizer for the gain in the gain-shape coding of residual + *---------------------------------------------------------------*/ + + float gainquant(/* (o) quantized gain value */ + float in, /* (i) gain value */ + float maxIn,/* (i) maximum of gain value */ + int cblen, /* (i) number of quantization indices */ + int *index /* (o) quantization index */ + ){ + int i, tindex; + float minmeasure,measure, *cb, scale; + + /* ensure a lower bound on the scaling factor */ + + scale=maxIn; + + if (scale<0.1) { + scale=(float)0.1; + } + + /* select the quantization table */ + + if (cblen == 8) { + cb = gain_sq3Tbl; + } else if (cblen == 16) { + cb = gain_sq4Tbl; + } else { + cb = gain_sq5Tbl; + } + + /* select the best index in the quantization table */ + + minmeasure=10000000.0; + tindex=0; + for (i=0; i<cblen; i++) { + + + +Andersen, et al. Experimental [Page 132] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + measure=(in-scale*cb[i])*(in-scale*cb[i]); + + if (measure<minmeasure) { + tindex=i; + minmeasure=measure; + } + } + *index=tindex; + + /* return the quantized value */ + + return scale*cb[tindex]; + } + + /*----------------------------------------------------------------* + * decoder for quantized gains in the gain-shape coding of + * residual + *---------------------------------------------------------------*/ + + float gaindequant( /* (o) quantized gain value */ + int index, /* (i) quantization index */ + float maxIn,/* (i) maximum of unquantized gain */ + int cblen /* (i) number of quantization indices */ + ){ + float scale; + + /* obtain correct scale factor */ + + scale=(float)fabs(maxIn); + + if (scale<0.1) { + scale=(float)0.1; + } + + /* select the quantization table and return the decoded value */ + + if (cblen==8) { + return scale*gain_sq3Tbl[index]; + } else if (cblen==16) { + return scale*gain_sq4Tbl[index]; + } + else if (cblen==32) { + return scale*gain_sq5Tbl[index]; + } + + return 0.0; + } + + + + +Andersen, et al. Experimental [Page 133] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + +A.23. getCBvec.h + + /****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + getCBvec.h + + Copyright (C) The Internet Society (2004). + All Rights Reserved. + + ******************************************************************/ + + #ifndef __iLBC_GETCBVEC_H + #define __iLBC_GETCBVEC_H + + void getCBvec( + float *cbvec, /* (o) Constructed codebook vector */ + float *mem, /* (i) Codebook buffer */ + int index, /* (i) Codebook index */ + int lMem, /* (i) Length of codebook buffer */ + int cbveclen/* (i) Codebook vector length */ + ); + + #endif + +A.24. getCBvec.c + + /****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + getCBvec.c + + Copyright (C) The Internet Society (2004). + All Rights Reserved. + + ******************************************************************/ + + #include "iLBC_define.h" + #include "constants.h" + #include <string.h> + + /*----------------------------------------------------------------* + * Construct codebook vector for given index. + *---------------------------------------------------------------*/ + + void getCBvec( + + + +Andersen, et al. Experimental [Page 134] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + float *cbvec, /* (o) Constructed codebook vector */ + float *mem, /* (i) Codebook buffer */ + int index, /* (i) Codebook index */ + int lMem, /* (i) Length of codebook buffer */ + int cbveclen/* (i) Codebook vector length */ + ){ + int j, k, n, memInd, sFilt; + float tmpbuf[CB_MEML]; + int base_size; + int ilow, ihigh; + float alfa, alfa1; + + /* Determine size of codebook sections */ + + base_size=lMem-cbveclen+1; + + if (cbveclen==SUBL) { + base_size+=cbveclen/2; + } + + /* No filter -> First codebook section */ + + if (index<lMem-cbveclen+1) { + + /* first non-interpolated vectors */ + + k=index+cbveclen; + /* get vector */ + memcpy(cbvec, mem+lMem-k, cbveclen*sizeof(float)); + + } else if (index < base_size) { + + k=2*(index-(lMem-cbveclen+1))+cbveclen; + + ihigh=k/2; + ilow=ihigh-5; + + /* Copy first noninterpolated part */ + + memcpy(cbvec, mem+lMem-k/2, ilow*sizeof(float)); + + /* interpolation */ + + alfa1=(float)0.2; + alfa=0.0; + for (j=ilow; j<ihigh; j++) { + cbvec[j]=((float)1.0-alfa)*mem[lMem-k/2+j]+ + alfa*mem[lMem-k+j]; + + + +Andersen, et al. Experimental [Page 135] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + alfa+=alfa1; + } + + /* Copy second noninterpolated part */ + + memcpy(cbvec+ihigh, mem+lMem-k+ihigh, + (cbveclen-ihigh)*sizeof(float)); + + } + + /* Higher codebook section based on filtering */ + + else { + + /* first non-interpolated vectors */ + + if (index-base_size<lMem-cbveclen+1) { + float tempbuff2[CB_MEML+CB_FILTERLEN+1]; + float *pos; + float *pp, *pp1; + + memset(tempbuff2, 0, + CB_HALFFILTERLEN*sizeof(float)); + memcpy(&tempbuff2[CB_HALFFILTERLEN], mem, + lMem*sizeof(float)); + memset(&tempbuff2[lMem+CB_HALFFILTERLEN], 0, + (CB_HALFFILTERLEN+1)*sizeof(float)); + + k=index-base_size+cbveclen; + sFilt=lMem-k; + memInd=sFilt+1-CB_HALFFILTERLEN; + + /* do filtering */ + pos=cbvec; + memset(pos, 0, cbveclen*sizeof(float)); + for (n=0; n<cbveclen; n++) { + pp=&tempbuff2[memInd+n+CB_HALFFILTERLEN]; + pp1=&cbfiltersTbl[CB_FILTERLEN-1]; + for (j=0; j<CB_FILTERLEN; j++) { + (*pos)+=(*pp++)*(*pp1--); + } + pos++; + } + } + + /* interpolated vectors */ + + else { + + + +Andersen, et al. Experimental [Page 136] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + float tempbuff2[CB_MEML+CB_FILTERLEN+1]; + + float *pos; + float *pp, *pp1; + int i; + + memset(tempbuff2, 0, + CB_HALFFILTERLEN*sizeof(float)); + memcpy(&tempbuff2[CB_HALFFILTERLEN], mem, + lMem*sizeof(float)); + memset(&tempbuff2[lMem+CB_HALFFILTERLEN], 0, + (CB_HALFFILTERLEN+1)*sizeof(float)); + + k=2*(index-base_size- + (lMem-cbveclen+1))+cbveclen; + sFilt=lMem-k; + memInd=sFilt+1-CB_HALFFILTERLEN; + + /* do filtering */ + pos=&tmpbuf[sFilt]; + memset(pos, 0, k*sizeof(float)); + for (i=0; i<k; i++) { + pp=&tempbuff2[memInd+i+CB_HALFFILTERLEN]; + pp1=&cbfiltersTbl[CB_FILTERLEN-1]; + for (j=0; j<CB_FILTERLEN; j++) { + (*pos)+=(*pp++)*(*pp1--); + } + pos++; + } + + ihigh=k/2; + ilow=ihigh-5; + + /* Copy first noninterpolated part */ + + memcpy(cbvec, tmpbuf+lMem-k/2, + ilow*sizeof(float)); + + /* interpolation */ + + alfa1=(float)0.2; + alfa=0.0; + for (j=ilow; j<ihigh; j++) { + cbvec[j]=((float)1.0-alfa)* + tmpbuf[lMem-k/2+j]+alfa*tmpbuf[lMem-k+j]; + alfa+=alfa1; + } + + + + +Andersen, et al. Experimental [Page 137] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + /* Copy second noninterpolated part */ + + memcpy(cbvec+ihigh, tmpbuf+lMem-k+ihigh, + (cbveclen-ihigh)*sizeof(float)); + } + } + } + +A.25. helpfun.h + + /****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + helpfun.h + + Copyright (C) The Internet Society (2004). + All Rights Reserved. + + ******************************************************************/ + + #ifndef __iLBC_HELPFUN_H + #define __iLBC_HELPFUN_H + + void autocorr( + float *r, /* (o) autocorrelation vector */ + const float *x, /* (i) data vector */ + int N, /* (i) length of data vector */ + int order /* largest lag for calculated + autocorrelations */ + ); + + void window( + float *z, /* (o) the windowed data */ + const float *x, /* (i) the original data vector */ + const float *y, /* (i) the window */ + int N /* (i) length of all vectors */ + ); + + void levdurb( + float *a, /* (o) lpc coefficient vector starting + with 1.0 */ + float *k, /* (o) reflection coefficients */ + float *r, /* (i) autocorrelation vector */ + int order /* (i) order of lpc filter */ + ); + + void interpolate( + + + +Andersen, et al. Experimental [Page 138] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + float *out, /* (o) the interpolated vector */ + float *in1, /* (i) the first vector for the + interpolation */ + float *in2, /* (i) the second vector for the + interpolation */ + float coef, /* (i) interpolation weights */ + int length /* (i) length of all vectors */ + ); + + void bwexpand( + float *out, /* (o) the bandwidth expanded lpc + coefficients */ + float *in, /* (i) the lpc coefficients before bandwidth + expansion */ + float coef, /* (i) the bandwidth expansion factor */ + int length /* (i) the length of lpc coefficient vectors */ + ); + + void vq( + float *Xq, /* (o) the quantized vector */ + int *index, /* (o) the quantization index */ + const float *CB,/* (i) the vector quantization codebook */ + float *X, /* (i) the vector to quantize */ + int n_cb, /* (i) the number of vectors in the codebook */ + int dim /* (i) the dimension of all vectors */ + ); + + void SplitVQ( + float *qX, /* (o) the quantized vector */ + int *index, /* (o) a vector of indexes for all vector + codebooks in the split */ + float *X, /* (i) the vector to quantize */ + const float *CB,/* (i) the quantizer codebook */ + int nsplit, /* the number of vector splits */ + const int *dim, /* the dimension of X and qX */ + const int *cbsize /* the number of vectors in the codebook */ + ); + + + void sort_sq( + float *xq, /* (o) the quantized value */ + int *index, /* (o) the quantization index */ + float x, /* (i) the value to quantize */ + const float *cb,/* (i) the quantization codebook */ + int cb_size /* (i) the size of the quantization codebook */ + ); + + int LSF_check( /* (o) 1 for stable lsf vectors and 0 for + + + +Andersen, et al. Experimental [Page 139] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + nonstable ones */ + float *lsf, /* (i) a table of lsf vectors */ + int dim, /* (i) the dimension of each lsf vector */ + int NoAn /* (i) the number of lsf vectors in the + table */ + ); + + #endif + +A.26. helpfun.c + + /****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + helpfun.c + + Copyright (C) The Internet Society (2004). + All Rights Reserved. + + ******************************************************************/ + + #include <math.h> + + #include "iLBC_define.h" + #include "constants.h" + + /*----------------------------------------------------------------* + * calculation of auto correlation + *---------------------------------------------------------------*/ + + void autocorr( + float *r, /* (o) autocorrelation vector */ + const float *x, /* (i) data vector */ + int N, /* (i) length of data vector */ + int order /* largest lag for calculated + autocorrelations */ + ){ + int lag, n; + float sum; + + for (lag = 0; lag <= order; lag++) { + sum = 0; + for (n = 0; n < N - lag; n++) { + sum += x[n] * x[n+lag]; + } + r[lag] = sum; + } + + + +Andersen, et al. Experimental [Page 140] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + } + + /*----------------------------------------------------------------* + * window multiplication + *---------------------------------------------------------------*/ + + void window( + float *z, /* (o) the windowed data */ + const float *x, /* (i) the original data vector */ + const float *y, /* (i) the window */ + int N /* (i) length of all vectors */ + ){ + int i; + + for (i = 0; i < N; i++) { + z[i] = x[i] * y[i]; + } + } + + /*----------------------------------------------------------------* + * levinson-durbin solution for lpc coefficients + *---------------------------------------------------------------*/ + + void levdurb( + float *a, /* (o) lpc coefficient vector starting + with 1.0 */ + float *k, /* (o) reflection coefficients */ + float *r, /* (i) autocorrelation vector */ + int order /* (i) order of lpc filter */ + ){ + float sum, alpha; + int m, m_h, i; + + a[0] = 1.0; + + if (r[0] < EPS) { /* if r[0] <= 0, set LPC coeff. to zero */ + for (i = 0; i < order; i++) { + k[i] = 0; + a[i+1] = 0; + } + } else { + a[1] = k[0] = -r[1]/r[0]; + alpha = r[0] + r[1] * k[0]; + for (m = 1; m < order; m++){ + sum = r[m + 1]; + for (i = 0; i < m; i++){ + sum += a[i+1] * r[m - i]; + } + + + +Andersen, et al. Experimental [Page 141] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + k[m] = -sum / alpha; + alpha += k[m] * sum; + m_h = (m + 1) >> 1; + for (i = 0; i < m_h; i++){ + sum = a[i+1] + k[m] * a[m - i]; + a[m - i] += k[m] * a[i+1]; + a[i+1] = sum; + } + a[m+1] = k[m]; + } + } + } + + /*----------------------------------------------------------------* + * interpolation between vectors + *---------------------------------------------------------------*/ + + void interpolate( + float *out, /* (o) the interpolated vector */ + float *in1, /* (i) the first vector for the + interpolation */ + float *in2, /* (i) the second vector for the + interpolation */ + float coef, /* (i) interpolation weights */ + int length /* (i) length of all vectors */ + ){ + int i; + float invcoef; + + invcoef = (float)1.0 - coef; + for (i = 0; i < length; i++) { + out[i] = coef * in1[i] + invcoef * in2[i]; + } + } + + /*----------------------------------------------------------------* + * lpc bandwidth expansion + *---------------------------------------------------------------*/ + + void bwexpand( + float *out, /* (o) the bandwidth expanded lpc + coefficients */ + float *in, /* (i) the lpc coefficients before bandwidth + expansion */ + float coef, /* (i) the bandwidth expansion factor */ + int length /* (i) the length of lpc coefficient vectors */ + ){ + int i; + + + +Andersen, et al. Experimental [Page 142] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + float chirp; + + chirp = coef; + + out[0] = in[0]; + for (i = 1; i < length; i++) { + out[i] = chirp * in[i]; + chirp *= coef; + } + } + + /*----------------------------------------------------------------* + * vector quantization + *---------------------------------------------------------------*/ + + void vq( + float *Xq, /* (o) the quantized vector */ + int *index, /* (o) the quantization index */ + const float *CB,/* (i) the vector quantization codebook */ + float *X, /* (i) the vector to quantize */ + int n_cb, /* (i) the number of vectors in the codebook */ + int dim /* (i) the dimension of all vectors */ + ){ + int i, j; + int pos, minindex; + float dist, tmp, mindist; + + pos = 0; + mindist = FLOAT_MAX; + minindex = 0; + for (j = 0; j < n_cb; j++) { + dist = X[0] - CB[pos]; + dist *= dist; + for (i = 1; i < dim; i++) { + tmp = X[i] - CB[pos + i]; + dist += tmp*tmp; + } + + if (dist < mindist) { + mindist = dist; + minindex = j; + } + pos += dim; + } + for (i = 0; i < dim; i++) { + Xq[i] = CB[minindex*dim + i]; + } + *index = minindex; + + + +Andersen, et al. Experimental [Page 143] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + } + + /*----------------------------------------------------------------* + * split vector quantization + *---------------------------------------------------------------*/ + + void SplitVQ( + float *qX, /* (o) the quantized vector */ + int *index, /* (o) a vector of indexes for all vector + codebooks in the split */ + float *X, /* (i) the vector to quantize */ + const float *CB,/* (i) the quantizer codebook */ + int nsplit, /* the number of vector splits */ + const int *dim, /* the dimension of X and qX */ + const int *cbsize /* the number of vectors in the codebook */ + ){ + int cb_pos, X_pos, i; + + cb_pos = 0; + X_pos= 0; + for (i = 0; i < nsplit; i++) { + vq(qX + X_pos, index + i, CB + cb_pos, X + X_pos, + cbsize[i], dim[i]); + X_pos += dim[i]; + cb_pos += dim[i] * cbsize[i]; + } + } + + /*----------------------------------------------------------------* + * scalar quantization + *---------------------------------------------------------------*/ + + void sort_sq( + float *xq, /* (o) the quantized value */ + int *index, /* (o) the quantization index */ + float x, /* (i) the value to quantize */ + const float *cb,/* (i) the quantization codebook */ + int cb_size /* (i) the size of the quantization codebook */ + ){ + int i; + + if (x <= cb[0]) { + *index = 0; + *xq = cb[0]; + } else { + i = 0; + while ((x > cb[i]) && i < cb_size - 1) { + i++; + + + +Andersen, et al. Experimental [Page 144] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + } + + if (x > ((cb[i] + cb[i - 1])/2)) { + *index = i; + *xq = cb[i]; + } else { + *index = i - 1; + *xq = cb[i - 1]; + } + } + } + + /*----------------------------------------------------------------* + * check for stability of lsf coefficients + *---------------------------------------------------------------*/ + + int LSF_check( /* (o) 1 for stable lsf vectors and 0 for + nonstable ones */ + float *lsf, /* (i) a table of lsf vectors */ + int dim, /* (i) the dimension of each lsf vector */ + int NoAn /* (i) the number of lsf vectors in the + table */ + ){ + int k,n,m, Nit=2, change=0,pos; + float tmp; + static float eps=(float)0.039; /* 50 Hz */ + static float eps2=(float)0.0195; + static float maxlsf=(float)3.14; /* 4000 Hz */ + static float minlsf=(float)0.01; /* 0 Hz */ + + /* LSF separation check*/ + + for (n=0; n<Nit; n++) { /* Run through a couple of times */ + for (m=0; m<NoAn; m++) { /* Number of analyses per frame */ + for (k=0; k<(dim-1); k++) { + pos=m*dim+k; + + if ((lsf[pos+1]-lsf[pos])<eps) { + + if (lsf[pos+1]<lsf[pos]) { + tmp=lsf[pos+1]; + lsf[pos+1]= lsf[pos]+eps2; + lsf[pos]= lsf[pos+1]-eps2; + } else { + lsf[pos]-=eps2; + lsf[pos+1]+=eps2; + } + change=1; + + + +Andersen, et al. Experimental [Page 145] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + } + + if (lsf[pos]<minlsf) { + lsf[pos]=minlsf; + change=1; + } + + if (lsf[pos]>maxlsf) { + lsf[pos]=maxlsf; + change=1; + } + } + } + } + + return change; + } + +A.27. hpInput.h + + /****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + hpInput.h + + Copyright (C) The Internet Society (2004). + All Rights Reserved. + + ******************************************************************/ + + #ifndef __iLBC_HPINPUT_H + #define __iLBC_HPINPUT_H + + void hpInput( + float *In, /* (i) vector to filter */ + int len, /* (i) length of vector to filter */ + float *Out, /* (o) the resulting filtered vector */ + float *mem /* (i/o) the filter state */ + ); + + #endif + +A.28. hpInput.c + + /****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + + +Andersen, et al. Experimental [Page 146] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + hpInput.c + + Copyright (C) The Internet Society (2004). + All Rights Reserved. + + ******************************************************************/ + + #include "constants.h" + + /*----------------------------------------------------------------* + * Input high-pass filter + *---------------------------------------------------------------*/ + + void hpInput( + float *In, /* (i) vector to filter */ + int len, /* (i) length of vector to filter */ + float *Out, /* (o) the resulting filtered vector */ + float *mem /* (i/o) the filter state */ + ){ + int i; + float *pi, *po; + + /* all-zero section*/ + + pi = &In[0]; + po = &Out[0]; + for (i=0; i<len; i++) { + *po = hpi_zero_coefsTbl[0] * (*pi); + *po += hpi_zero_coefsTbl[1] * mem[0]; + *po += hpi_zero_coefsTbl[2] * mem[1]; + + mem[1] = mem[0]; + mem[0] = *pi; + po++; + pi++; + + } + + /* all-pole section*/ + + po = &Out[0]; + for (i=0; i<len; i++) { + *po -= hpi_pole_coefsTbl[1] * mem[2]; + *po -= hpi_pole_coefsTbl[2] * mem[3]; + + mem[3] = mem[2]; + mem[2] = *po; + po++; + + + +Andersen, et al. Experimental [Page 147] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + } + } + +A.29. hpOutput.h + + /****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + hpOutput.h + + Copyright (C) The Internet Society (2004). + All Rights Reserved. + + ******************************************************************/ + + #ifndef __iLBC_HPOUTPUT_H + #define __iLBC_HPOUTPUT_H + + void hpOutput( + float *In, /* (i) vector to filter */ + int len,/* (i) length of vector to filter */ + float *Out, /* (o) the resulting filtered vector */ + float *mem /* (i/o) the filter state */ + ); + + #endif + +A.30. hpOutput.c + + /****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + hpOutput.c + + Copyright (C) The Internet Society (2004). + All Rights Reserved. + + ******************************************************************/ + + #include "constants.h" + + /*----------------------------------------------------------------* + * Output high-pass filter + *---------------------------------------------------------------*/ + + void hpOutput( + + + +Andersen, et al. Experimental [Page 148] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + float *In, /* (i) vector to filter */ + int len,/* (i) length of vector to filter */ + float *Out, /* (o) the resulting filtered vector */ + float *mem /* (i/o) the filter state */ + ){ + int i; + float *pi, *po; + + /* all-zero section*/ + + pi = &In[0]; + po = &Out[0]; + for (i=0; i<len; i++) { + *po = hpo_zero_coefsTbl[0] * (*pi); + *po += hpo_zero_coefsTbl[1] * mem[0]; + *po += hpo_zero_coefsTbl[2] * mem[1]; + + mem[1] = mem[0]; + mem[0] = *pi; + po++; + pi++; + + } + + /* all-pole section*/ + + po = &Out[0]; + for (i=0; i<len; i++) { + *po -= hpo_pole_coefsTbl[1] * mem[2]; + *po -= hpo_pole_coefsTbl[2] * mem[3]; + + mem[3] = mem[2]; + mem[2] = *po; + po++; + } + } + +A.31. iCBConstruct.h + + /****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + iCBConstruct.h + + Copyright (C) The Internet Society (2004). + All Rights Reserved. + + + + +Andersen, et al. Experimental [Page 149] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + ******************************************************************/ + + #ifndef __iLBC_ICBCONSTRUCT_H + #define __iLBC_ICBCONSTRUCT_H + + void index_conv_enc( + int *index /* (i/o) Codebook indexes */ + ); + + void index_conv_dec( + int *index /* (i/o) Codebook indexes */ + ); + + void iCBConstruct( + float *decvector, /* (o) Decoded vector */ + int *index, /* (i) Codebook indices */ + int *gain_index,/* (i) Gain quantization indices */ + float *mem, /* (i) Buffer for codevector construction */ + int lMem, /* (i) Length of buffer */ + int veclen, /* (i) Length of vector */ + int nStages /* (i) Number of codebook stages */ + ); + + #endif + +A.32. iCBConstruct.c + + /****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + iCBConstruct.c + + Copyright (C) The Internet Society (2004). + All Rights Reserved. + + ******************************************************************/ + + #include <math.h> + + #include "iLBC_define.h" + #include "gainquant.h" + #include "getCBvec.h" + + /*----------------------------------------------------------------* + * Convert the codebook indexes to make the search easier + *---------------------------------------------------------------*/ + + + + +Andersen, et al. Experimental [Page 150] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + void index_conv_enc( + int *index /* (i/o) Codebook indexes */ + ){ + int k; + + for (k=1; k<CB_NSTAGES; k++) { + + if ((index[k]>=108)&&(index[k]<172)) { + index[k]-=64; + } else if (index[k]>=236) { + index[k]-=128; + } else { + /* ERROR */ + } + } + } + + void index_conv_dec( + int *index /* (i/o) Codebook indexes */ + ){ + int k; + + for (k=1; k<CB_NSTAGES; k++) { + + if ((index[k]>=44)&&(index[k]<108)) { + index[k]+=64; + } else if ((index[k]>=108)&&(index[k]<128)) { + index[k]+=128; + } else { + /* ERROR */ + } + } + } + + /*----------------------------------------------------------------* + * Construct decoded vector from codebook and gains. + *---------------------------------------------------------------*/ + + void iCBConstruct( + float *decvector, /* (o) Decoded vector */ + int *index, /* (i) Codebook indices */ + int *gain_index,/* (i) Gain quantization indices */ + float *mem, /* (i) Buffer for codevector construction */ + int lMem, /* (i) Length of buffer */ + int veclen, /* (i) Length of vector */ + int nStages /* (i) Number of codebook stages */ + ){ + int j,k; + + + +Andersen, et al. Experimental [Page 151] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + float gain[CB_NSTAGES]; + float cbvec[SUBL]; + + /* gain de-quantization */ + + gain[0] = gaindequant(gain_index[0], 1.0, 32); + if (nStages > 1) { + gain[1] = gaindequant(gain_index[1], + (float)fabs(gain[0]), 16); + } + if (nStages > 2) { + gain[2] = gaindequant(gain_index[2], + (float)fabs(gain[1]), 8); + } + + /* codebook vector construction and construction of + total vector */ + + getCBvec(cbvec, mem, index[0], lMem, veclen); + for (j=0;j<veclen;j++){ + decvector[j] = gain[0]*cbvec[j]; + } + if (nStages > 1) { + for (k=1; k<nStages; k++) { + getCBvec(cbvec, mem, index[k], lMem, veclen); + for (j=0;j<veclen;j++) { + decvector[j] += gain[k]*cbvec[j]; + } + } + } + } + +A.33. iCBSearch.h + + /****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + iCBSearch.h + + Copyright (C) The Internet Society (2004). + All Rights Reserved. + + ******************************************************************/ + + #ifndef __iLBC_ICBSEARCH_H + #define __iLBC_ICBSEARCH_H + + + + +Andersen, et al. Experimental [Page 152] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + void iCBSearch( + iLBC_Enc_Inst_t *iLBCenc_inst, + /* (i) the encoder state structure */ + int *index, /* (o) Codebook indices */ + int *gain_index,/* (o) Gain quantization indices */ + float *intarget,/* (i) Target vector for encoding */ + float *mem, /* (i) Buffer for codebook construction */ + int lMem, /* (i) Length of buffer */ + int lTarget, /* (i) Length of vector */ + int nStages, /* (i) Number of codebook stages */ + float *weightDenum, /* (i) weighting filter coefficients */ + float *weightState, /* (i) weighting filter state */ + int block /* (i) the sub-block number */ + ); + + #endif + +A.34. iCBSearch.c + + /****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + iCBSearch.c + + Copyright (C) The Internet Society (2004). + All Rights Reserved. + + ******************************************************************/ + + #include <math.h> + #include <string.h> + + #include "iLBC_define.h" + #include "gainquant.h" + #include "createCB.h" + #include "filter.h" + #include "constants.h" + + /*----------------------------------------------------------------* + * Search routine for codebook encoding and gain quantization. + *---------------------------------------------------------------*/ + + void iCBSearch( + iLBC_Enc_Inst_t *iLBCenc_inst, + /* (i) the encoder state structure */ + int *index, /* (o) Codebook indices */ + int *gain_index,/* (o) Gain quantization indices */ + + + +Andersen, et al. Experimental [Page 153] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + float *intarget,/* (i) Target vector for encoding */ + float *mem, /* (i) Buffer for codebook construction */ + int lMem, /* (i) Length of buffer */ + int lTarget, /* (i) Length of vector */ + int nStages, /* (i) Number of codebook stages */ + float *weightDenum, /* (i) weighting filter coefficients */ + float *weightState, /* (i) weighting filter state */ + int block /* (i) the sub-block number */ + ){ + int i, j, icount, stage, best_index, range, counter; + float max_measure, gain, measure, crossDot, ftmp; + float gains[CB_NSTAGES]; + float target[SUBL]; + int base_index, sInd, eInd, base_size; + int sIndAug=0, eIndAug=0; + float buf[CB_MEML+SUBL+2*LPC_FILTERORDER]; + float invenergy[CB_EXPAND*128], energy[CB_EXPAND*128]; + float *pp, *ppi=0, *ppo=0, *ppe=0; + float cbvectors[CB_MEML]; + float tene, cene, cvec[SUBL]; + float aug_vec[SUBL]; + + memset(cvec,0,SUBL*sizeof(float)); + + /* Determine size of codebook sections */ + + base_size=lMem-lTarget+1; + + if (lTarget==SUBL) { + base_size=lMem-lTarget+1+lTarget/2; + } + + /* setup buffer for weighting */ + + memcpy(buf,weightState,sizeof(float)*LPC_FILTERORDER); + memcpy(buf+LPC_FILTERORDER,mem,lMem*sizeof(float)); + memcpy(buf+LPC_FILTERORDER+lMem,intarget,lTarget*sizeof(float)); + + /* weighting */ + + AllPoleFilter(buf+LPC_FILTERORDER, weightDenum, + lMem+lTarget, LPC_FILTERORDER); + + /* Construct the codebook and target needed */ + + memcpy(target, buf+LPC_FILTERORDER+lMem, lTarget*sizeof(float)); + + tene=0.0; + + + +Andersen, et al. Experimental [Page 154] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + for (i=0; i<lTarget; i++) { + tene+=target[i]*target[i]; + } + + /* Prepare search over one more codebook section. This section + is created by filtering the original buffer with a filter. */ + + filteredCBvecs(cbvectors, buf+LPC_FILTERORDER, lMem); + + /* The Main Loop over stages */ + + for (stage=0; stage<nStages; stage++) { + + range = search_rangeTbl[block][stage]; + + /* initialize search measure */ + + max_measure = (float)-10000000.0; + gain = (float)0.0; + best_index = 0; + + /* Compute cross dot product between the target + and the CB memory */ + + crossDot=0.0; + pp=buf+LPC_FILTERORDER+lMem-lTarget; + for (j=0; j<lTarget; j++) { + crossDot += target[j]*(*pp++); + } + + if (stage==0) { + + /* Calculate energy in the first block of + 'lTarget' samples. */ + ppe = energy; + ppi = buf+LPC_FILTERORDER+lMem-lTarget-1; + ppo = buf+LPC_FILTERORDER+lMem-1; + + *ppe=0.0; + pp=buf+LPC_FILTERORDER+lMem-lTarget; + for (j=0; j<lTarget; j++) { + *ppe+=(*pp)*(*pp++); + } + + if (*ppe>0.0) { + invenergy[0] = (float) 1.0 / (*ppe + EPS); + } else { + invenergy[0] = (float) 0.0; + + + +Andersen, et al. Experimental [Page 155] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + } + ppe++; + + measure=(float)-10000000.0; + + if (crossDot > 0.0) { + measure = crossDot*crossDot*invenergy[0]; + } + } + else { + measure = crossDot*crossDot*invenergy[0]; + } + + /* check if measure is better */ + ftmp = crossDot*invenergy[0]; + + if ((measure>max_measure) && (fabs(ftmp)<CB_MAXGAIN)) { + best_index = 0; + max_measure = measure; + gain = ftmp; + } + + /* loop over the main first codebook section, + full search */ + + for (icount=1; icount<range; icount++) { + + /* calculate measure */ + + crossDot=0.0; + pp = buf+LPC_FILTERORDER+lMem-lTarget-icount; + + for (j=0; j<lTarget; j++) { + crossDot += target[j]*(*pp++); + } + + if (stage==0) { + *ppe++ = energy[icount-1] + (*ppi)*(*ppi) - + (*ppo)*(*ppo); + ppo--; + ppi--; + + if (energy[icount]>0.0) { + invenergy[icount] = + (float)1.0/(energy[icount]+EPS); + } else { + invenergy[icount] = (float) 0.0; + } + + + +Andersen, et al. Experimental [Page 156] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + measure=(float)-10000000.0; + + if (crossDot > 0.0) { + measure = crossDot*crossDot*invenergy[icount]; + } + } + else { + measure = crossDot*crossDot*invenergy[icount]; + } + + /* check if measure is better */ + ftmp = crossDot*invenergy[icount]; + + if ((measure>max_measure) && (fabs(ftmp)<CB_MAXGAIN)) { + best_index = icount; + max_measure = measure; + gain = ftmp; + } + } + + /* Loop over augmented part in the first codebook + * section, full search. + * The vectors are interpolated. + */ + + if (lTarget==SUBL) { + + /* Search for best possible cb vector and + compute the CB-vectors' energy. */ + searchAugmentedCB(20, 39, stage, base_size-lTarget/2, + target, buf+LPC_FILTERORDER+lMem, + &max_measure, &best_index, &gain, energy, + invenergy); + } + + /* set search range for following codebook sections */ + + base_index=best_index; + + /* unrestricted search */ + + if (CB_RESRANGE == -1) { + sInd=0; + eInd=range-1; + sIndAug=20; + eIndAug=39; + } + + + + +Andersen, et al. Experimental [Page 157] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + /* restricted search around best index from first + codebook section */ + + else { + /* Initialize search indices */ + sIndAug=0; + eIndAug=0; + sInd=base_index-CB_RESRANGE/2; + eInd=sInd+CB_RESRANGE; + + if (lTarget==SUBL) { + + if (sInd<0) { + + sIndAug = 40 + sInd; + eIndAug = 39; + sInd=0; + + } else if ( base_index < (base_size-20) ) { + + if (eInd > range) { + sInd -= (eInd-range); + eInd = range; + } + } else { /* base_index >= (base_size-20) */ + + if (sInd < (base_size-20)) { + sIndAug = 20; + sInd = 0; + eInd = 0; + eIndAug = 19 + CB_RESRANGE; + + if(eIndAug > 39) { + eInd = eIndAug-39; + eIndAug = 39; + } + } else { + sIndAug = 20 + sInd - (base_size-20); + eIndAug = 39; + sInd = 0; + eInd = CB_RESRANGE - (eIndAug-sIndAug+1); + } + } + + } else { /* lTarget = 22 or 23 */ + + if (sInd < 0) { + eInd -= sInd; + + + +Andersen, et al. Experimental [Page 158] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + sInd = 0; + } + + if(eInd > range) { + sInd -= (eInd - range); + eInd = range; + } + } + } + + /* search of higher codebook section */ + + /* index search range */ + counter = sInd; + sInd += base_size; + eInd += base_size; + + + if (stage==0) { + ppe = energy+base_size; + *ppe=0.0; + + pp=cbvectors+lMem-lTarget; + for (j=0; j<lTarget; j++) { + *ppe+=(*pp)*(*pp++); + } + + ppi = cbvectors + lMem - 1 - lTarget; + ppo = cbvectors + lMem - 1; + + for (j=0; j<(range-1); j++) { + *(ppe+1) = *ppe + (*ppi)*(*ppi) - (*ppo)*(*ppo); + ppo--; + ppi--; + ppe++; + } + } + + /* loop over search range */ + + for (icount=sInd; icount<eInd; icount++) { + + /* calculate measure */ + + crossDot=0.0; + pp=cbvectors + lMem - (counter++) - lTarget; + + for (j=0;j<lTarget;j++) { + + + +Andersen, et al. Experimental [Page 159] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + crossDot += target[j]*(*pp++); + } + + if (energy[icount]>0.0) { + invenergy[icount] =(float)1.0/(energy[icount]+EPS); + } else { + invenergy[icount] =(float)0.0; + } + + if (stage==0) { + + measure=(float)-10000000.0; + + if (crossDot > 0.0) { + measure = crossDot*crossDot* + invenergy[icount]; + } + } + else { + measure = crossDot*crossDot*invenergy[icount]; + } + + /* check if measure is better */ + ftmp = crossDot*invenergy[icount]; + + if ((measure>max_measure) && (fabs(ftmp)<CB_MAXGAIN)) { + best_index = icount; + max_measure = measure; + gain = ftmp; + } + } + + /* Search the augmented CB inside the limited range. */ + + if ((lTarget==SUBL)&&(sIndAug!=0)) { + searchAugmentedCB(sIndAug, eIndAug, stage, + 2*base_size-20, target, cbvectors+lMem, + &max_measure, &best_index, &gain, energy, + invenergy); + } + + /* record best index */ + + index[stage] = best_index; + + /* gain quantization */ + + if (stage==0){ + + + +Andersen, et al. Experimental [Page 160] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + + if (gain<0.0){ + gain = 0.0; + } + + if (gain>CB_MAXGAIN) { + gain = (float)CB_MAXGAIN; + } + gain = gainquant(gain, 1.0, 32, &gain_index[stage]); + } + else { + if (stage==1) { + gain = gainquant(gain, (float)fabs(gains[stage-1]), + 16, &gain_index[stage]); + } else { + gain = gainquant(gain, (float)fabs(gains[stage-1]), + 8, &gain_index[stage]); + } + } + + /* Extract the best (according to measure) + codebook vector */ + + if (lTarget==(STATE_LEN-iLBCenc_inst->state_short_len)) { + + if (index[stage]<base_size) { + pp=buf+LPC_FILTERORDER+lMem-lTarget-index[stage]; + } else { + pp=cbvectors+lMem-lTarget- + index[stage]+base_size; + } + } else { + + if (index[stage]<base_size) { + if (index[stage]<(base_size-20)) { + pp=buf+LPC_FILTERORDER+lMem- + lTarget-index[stage]; + } else { + createAugmentedVec(index[stage]-base_size+40, + buf+LPC_FILTERORDER+lMem,aug_vec); + pp=aug_vec; + } + } else { + int filterno, position; + + filterno=index[stage]/base_size; + position=index[stage]-filterno*base_size; + + + + +Andersen, et al. Experimental [Page 161] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + + if (position<(base_size-20)) { + pp=cbvectors+filterno*lMem-lTarget- + index[stage]+filterno*base_size; + } else { + createAugmentedVec( + index[stage]-(filterno+1)*base_size+40, + cbvectors+filterno*lMem,aug_vec); + pp=aug_vec; + } + } + } + + /* Subtract the best codebook vector, according + to measure, from the target vector */ + + for (j=0;j<lTarget;j++) { + cvec[j] += gain*(*pp); + target[j] -= gain*(*pp++); + } + + /* record quantized gain */ + + gains[stage]=gain; + + }/* end of Main Loop. for (stage=0;... */ + + /* Gain adjustment for energy matching */ + cene=0.0; + for (i=0; i<lTarget; i++) { + cene+=cvec[i]*cvec[i]; + } + j=gain_index[0]; + + for (i=gain_index[0]; i<32; i++) { + ftmp=cene*gain_sq5Tbl[i]*gain_sq5Tbl[i]; + + if ((ftmp<(tene*gains[0]*gains[0])) && + (gain_sq5Tbl[j]<(2.0*gains[0]))) { + j=i; + } + } + gain_index[0]=j; + } + + + + + + + +Andersen, et al. Experimental [Page 162] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + +A.35. LPCdecode.h + + /****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + LPC_decode.h + + Copyright (C) The Internet Society (2004). + All Rights Reserved. + + ******************************************************************/ + + #ifndef __iLBC_LPC_DECODE_H + #define __iLBC_LPC_DECODE_H + + void LSFinterpolate2a_dec( + float *a, /* (o) lpc coefficients for a sub-frame */ + float *lsf1, /* (i) first lsf coefficient vector */ + float *lsf2, /* (i) second lsf coefficient vector */ + float coef, /* (i) interpolation weight */ + int length /* (i) length of lsf vectors */ + ); + + void SimplelsfDEQ( + float *lsfdeq, /* (o) dequantized lsf coefficients */ + int *index, /* (i) quantization index */ + int lpc_n /* (i) number of LPCs */ + ); + + void DecoderInterpolateLSF( + float *syntdenum, /* (o) synthesis filter coefficients */ + float *weightdenum, /* (o) weighting denumerator + coefficients */ + float *lsfdeq, /* (i) dequantized lsf coefficients */ + int length, /* (i) length of lsf coefficient vector */ + iLBC_Dec_Inst_t *iLBCdec_inst + /* (i) the decoder state structure */ + ); + + #endif + + + + + + + + + + +Andersen, et al. Experimental [Page 163] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + +A.36. LPCdecode.c + + /****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + LPC_decode.c + + Copyright (C) The Internet Society (2004). + All Rights Reserved. + + ******************************************************************/ + + #include <math.h> + #include <string.h> + + #include "helpfun.h" + #include "lsf.h" + #include "iLBC_define.h" + #include "constants.h" + + /*---------------------------------------------------------------* + * interpolation of lsf coefficients for the decoder + *--------------------------------------------------------------*/ + + void LSFinterpolate2a_dec( + float *a, /* (o) lpc coefficients for a sub-frame */ + float *lsf1, /* (i) first lsf coefficient vector */ + float *lsf2, /* (i) second lsf coefficient vector */ + float coef, /* (i) interpolation weight */ + int length /* (i) length of lsf vectors */ + ){ + float lsftmp[LPC_FILTERORDER]; + + interpolate(lsftmp, lsf1, lsf2, coef, length); + lsf2a(a, lsftmp); + } + + /*---------------------------------------------------------------* + * obtain dequantized lsf coefficients from quantization index + *--------------------------------------------------------------*/ + + void SimplelsfDEQ( + float *lsfdeq, /* (o) dequantized lsf coefficients */ + int *index, /* (i) quantization index */ + int lpc_n /* (i) number of LPCs */ + ){ + int i, j, pos, cb_pos; + + + +Andersen, et al. Experimental [Page 164] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + /* decode first LSF */ + + pos = 0; + cb_pos = 0; + for (i = 0; i < LSF_NSPLIT; i++) { + for (j = 0; j < dim_lsfCbTbl[i]; j++) { + lsfdeq[pos + j] = lsfCbTbl[cb_pos + + (long)(index[i])*dim_lsfCbTbl[i] + j]; + } + pos += dim_lsfCbTbl[i]; + cb_pos += size_lsfCbTbl[i]*dim_lsfCbTbl[i]; + } + + if (lpc_n>1) { + + /* decode last LSF */ + + pos = 0; + cb_pos = 0; + for (i = 0; i < LSF_NSPLIT; i++) { + for (j = 0; j < dim_lsfCbTbl[i]; j++) { + lsfdeq[LPC_FILTERORDER + pos + j] = + lsfCbTbl[cb_pos + + (long)(index[LSF_NSPLIT + i])* + dim_lsfCbTbl[i] + j]; + } + pos += dim_lsfCbTbl[i]; + cb_pos += size_lsfCbTbl[i]*dim_lsfCbTbl[i]; + } + } + } + + /*----------------------------------------------------------------* + * obtain synthesis and weighting filters form lsf coefficients + *---------------------------------------------------------------*/ + + void DecoderInterpolateLSF( + float *syntdenum, /* (o) synthesis filter coefficients */ + float *weightdenum, /* (o) weighting denumerator + coefficients */ + float *lsfdeq, /* (i) dequantized lsf coefficients */ + int length, /* (i) length of lsf coefficient vector */ + iLBC_Dec_Inst_t *iLBCdec_inst + /* (i) the decoder state structure */ + ){ + int i, pos, lp_length; + float lp[LPC_FILTERORDER + 1], *lsfdeq2; + + + + +Andersen, et al. Experimental [Page 165] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + lsfdeq2 = lsfdeq + length; + lp_length = length + 1; + + if (iLBCdec_inst->mode==30) { + /* sub-frame 1: Interpolation between old and first */ + + LSFinterpolate2a_dec(lp, iLBCdec_inst->lsfdeqold, lsfdeq, + lsf_weightTbl_30ms[0], length); + memcpy(syntdenum,lp,lp_length*sizeof(float)); + bwexpand(weightdenum, lp, LPC_CHIRP_WEIGHTDENUM, + lp_length); + + /* sub-frames 2 to 6: interpolation between first + and last LSF */ + + pos = lp_length; + for (i = 1; i < 6; i++) { + LSFinterpolate2a_dec(lp, lsfdeq, lsfdeq2, + lsf_weightTbl_30ms[i], length); + memcpy(syntdenum + pos,lp,lp_length*sizeof(float)); + bwexpand(weightdenum + pos, lp, + LPC_CHIRP_WEIGHTDENUM, lp_length); + pos += lp_length; + } + } + else { + pos = 0; + for (i = 0; i < iLBCdec_inst->nsub; i++) { + LSFinterpolate2a_dec(lp, iLBCdec_inst->lsfdeqold, + lsfdeq, lsf_weightTbl_20ms[i], length); + memcpy(syntdenum+pos,lp,lp_length*sizeof(float)); + bwexpand(weightdenum+pos, lp, LPC_CHIRP_WEIGHTDENUM, + lp_length); + pos += lp_length; + } + } + + /* update memory */ + + if (iLBCdec_inst->mode==30) + memcpy(iLBCdec_inst->lsfdeqold, lsfdeq2, + length*sizeof(float)); + else + memcpy(iLBCdec_inst->lsfdeqold, lsfdeq, + length*sizeof(float)); + + } + + + + +Andersen, et al. Experimental [Page 166] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + +A.37. LPCencode.h + + /****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + LPCencode.h + + Copyright (C) The Internet Society (2004). + All Rights Reserved. + + ******************************************************************/ + + #ifndef __iLBC_LPCENCOD_H + #define __iLBC_LPCENCOD_H + + void LPCencode( + float *syntdenum, /* (i/o) synthesis filter coefficients + before/after encoding */ + float *weightdenum, /* (i/o) weighting denumerator coefficients + before/after encoding */ + int *lsf_index, /* (o) lsf quantization index */ + float *data, /* (i) lsf coefficients to quantize */ + iLBC_Enc_Inst_t *iLBCenc_inst + /* (i/o) the encoder state structure */ + ); + + #endif + +A.38. LPCencode.c + + /****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + LPCencode.c + + Copyright (C) The Internet Society (2004). + All Rights Reserved. + + ******************************************************************/ + + #include <string.h> + + #include "iLBC_define.h" + #include "helpfun.h" + #include "lsf.h" + #include "constants.h" + + + +Andersen, et al. Experimental [Page 167] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + /*----------------------------------------------------------------* + * lpc analysis (subrutine to LPCencode) + *---------------------------------------------------------------*/ + + void SimpleAnalysis( + float *lsf, /* (o) lsf coefficients */ + float *data, /* (i) new data vector */ + iLBC_Enc_Inst_t *iLBCenc_inst + /* (i/o) the encoder state structure */ + ){ + int k, is; + float temp[BLOCKL_MAX], lp[LPC_FILTERORDER + 1]; + float lp2[LPC_FILTERORDER + 1]; + float r[LPC_FILTERORDER + 1]; + + is=LPC_LOOKBACK+BLOCKL_MAX-iLBCenc_inst->blockl; + memcpy(iLBCenc_inst->lpc_buffer+is,data, + iLBCenc_inst->blockl*sizeof(float)); + + /* No lookahead, last window is asymmetric */ + + for (k = 0; k < iLBCenc_inst->lpc_n; k++) { + + is = LPC_LOOKBACK; + + if (k < (iLBCenc_inst->lpc_n - 1)) { + window(temp, lpc_winTbl, + iLBCenc_inst->lpc_buffer, BLOCKL_MAX); + } else { + window(temp, lpc_asymwinTbl, + iLBCenc_inst->lpc_buffer + is, BLOCKL_MAX); + } + + autocorr(r, temp, BLOCKL_MAX, LPC_FILTERORDER); + window(r, r, lpc_lagwinTbl, LPC_FILTERORDER + 1); + + levdurb(lp, temp, r, LPC_FILTERORDER); + bwexpand(lp2, lp, LPC_CHIRP_SYNTDENUM, LPC_FILTERORDER+1); + + a2lsf(lsf + k*LPC_FILTERORDER, lp2); + } + is=LPC_LOOKBACK+BLOCKL_MAX-iLBCenc_inst->blockl; + memmove(iLBCenc_inst->lpc_buffer, + iLBCenc_inst->lpc_buffer+LPC_LOOKBACK+BLOCKL_MAX-is, + is*sizeof(float)); + } + + /*----------------------------------------------------------------* + + + +Andersen, et al. Experimental [Page 168] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + * lsf interpolator and conversion from lsf to a coefficients + * (subrutine to SimpleInterpolateLSF) + *---------------------------------------------------------------*/ + + void LSFinterpolate2a_enc( + float *a, /* (o) lpc coefficients */ + float *lsf1,/* (i) first set of lsf coefficients */ + float *lsf2,/* (i) second set of lsf coefficients */ + float coef, /* (i) weighting coefficient to use between + lsf1 and lsf2 */ + long length /* (i) length of coefficient vectors */ + ){ + float lsftmp[LPC_FILTERORDER]; + + interpolate(lsftmp, lsf1, lsf2, coef, length); + lsf2a(a, lsftmp); + } + + /*----------------------------------------------------------------* + * lsf interpolator (subrutine to LPCencode) + *---------------------------------------------------------------*/ + + void SimpleInterpolateLSF( + float *syntdenum, /* (o) the synthesis filter denominator + resulting from the quantized + interpolated lsf */ + float *weightdenum, /* (o) the weighting filter denominator + resulting from the unquantized + interpolated lsf */ + float *lsf, /* (i) the unquantized lsf coefficients */ + float *lsfdeq, /* (i) the dequantized lsf coefficients */ + float *lsfold, /* (i) the unquantized lsf coefficients of + the previous signal frame */ + float *lsfdeqold, /* (i) the dequantized lsf coefficients of + the previous signal frame */ + int length, /* (i) should equate LPC_FILTERORDER */ + iLBC_Enc_Inst_t *iLBCenc_inst + /* (i/o) the encoder state structure */ + ){ + int i, pos, lp_length; + float lp[LPC_FILTERORDER + 1], *lsf2, *lsfdeq2; + + lsf2 = lsf + length; + lsfdeq2 = lsfdeq + length; + lp_length = length + 1; + + if (iLBCenc_inst->mode==30) { + /* sub-frame 1: Interpolation between old and first + + + +Andersen, et al. Experimental [Page 169] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + set of lsf coefficients */ + + LSFinterpolate2a_enc(lp, lsfdeqold, lsfdeq, + lsf_weightTbl_30ms[0], length); + memcpy(syntdenum,lp,lp_length*sizeof(float)); + LSFinterpolate2a_enc(lp, lsfold, lsf, + lsf_weightTbl_30ms[0], length); + bwexpand(weightdenum, lp, LPC_CHIRP_WEIGHTDENUM, lp_length); + + /* sub-frame 2 to 6: Interpolation between first + and second set of lsf coefficients */ + + pos = lp_length; + for (i = 1; i < iLBCenc_inst->nsub; i++) { + LSFinterpolate2a_enc(lp, lsfdeq, lsfdeq2, + lsf_weightTbl_30ms[i], length); + memcpy(syntdenum + pos,lp,lp_length*sizeof(float)); + + LSFinterpolate2a_enc(lp, lsf, lsf2, + lsf_weightTbl_30ms[i], length); + bwexpand(weightdenum + pos, lp, + LPC_CHIRP_WEIGHTDENUM, lp_length); + pos += lp_length; + } + } + else { + pos = 0; + for (i = 0; i < iLBCenc_inst->nsub; i++) { + LSFinterpolate2a_enc(lp, lsfdeqold, lsfdeq, + lsf_weightTbl_20ms[i], length); + memcpy(syntdenum+pos,lp,lp_length*sizeof(float)); + LSFinterpolate2a_enc(lp, lsfold, lsf, + lsf_weightTbl_20ms[i], length); + bwexpand(weightdenum+pos, lp, + LPC_CHIRP_WEIGHTDENUM, lp_length); + pos += lp_length; + } + } + + /* update memory */ + + if (iLBCenc_inst->mode==30) { + memcpy(lsfold, lsf2, length*sizeof(float)); + memcpy(lsfdeqold, lsfdeq2, length*sizeof(float)); + } + else { + memcpy(lsfold, lsf, length*sizeof(float)); + memcpy(lsfdeqold, lsfdeq, length*sizeof(float)); + + + +Andersen, et al. Experimental [Page 170] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + } + } + + /*----------------------------------------------------------------* + * lsf quantizer (subrutine to LPCencode) + *---------------------------------------------------------------*/ + + void SimplelsfQ( + float *lsfdeq, /* (o) dequantized lsf coefficients + (dimension FILTERORDER) */ + int *index, /* (o) quantization index */ + float *lsf, /* (i) the lsf coefficient vector to be + quantized (dimension FILTERORDER ) */ + int lpc_n /* (i) number of lsf sets to quantize */ + ){ + /* Quantize first LSF with memoryless split VQ */ + SplitVQ(lsfdeq, index, lsf, lsfCbTbl, LSF_NSPLIT, + dim_lsfCbTbl, size_lsfCbTbl); + + if (lpc_n==2) { + /* Quantize second LSF with memoryless split VQ */ + SplitVQ(lsfdeq + LPC_FILTERORDER, index + LSF_NSPLIT, + lsf + LPC_FILTERORDER, lsfCbTbl, LSF_NSPLIT, + dim_lsfCbTbl, size_lsfCbTbl); + } + } + + /*----------------------------------------------------------------* + * lpc encoder + *---------------------------------------------------------------*/ + + void LPCencode( + float *syntdenum, /* (i/o) synthesis filter coefficients + before/after encoding */ + float *weightdenum, /* (i/o) weighting denumerator + coefficients before/after + encoding */ + int *lsf_index, /* (o) lsf quantization index */ + float *data, /* (i) lsf coefficients to quantize */ + iLBC_Enc_Inst_t *iLBCenc_inst + /* (i/o) the encoder state structure */ + ){ + float lsf[LPC_FILTERORDER * LPC_N_MAX]; + float lsfdeq[LPC_FILTERORDER * LPC_N_MAX]; + int change=0; + + SimpleAnalysis(lsf, data, iLBCenc_inst); + SimplelsfQ(lsfdeq, lsf_index, lsf, iLBCenc_inst->lpc_n); + + + +Andersen, et al. Experimental [Page 171] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + change=LSF_check(lsfdeq, LPC_FILTERORDER, iLBCenc_inst->lpc_n); + SimpleInterpolateLSF(syntdenum, weightdenum, + lsf, lsfdeq, iLBCenc_inst->lsfold, + iLBCenc_inst->lsfdeqold, LPC_FILTERORDER, iLBCenc_inst); + } + +A.39. lsf.h + + /****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + lsf.h + + Copyright (C) The Internet Society (2004). + All Rights Reserved. + + ******************************************************************/ + + #ifndef __iLBC_LSF_H + #define __iLBC_LSF_H + + void a2lsf( + float *freq,/* (o) lsf coefficients */ + float *a /* (i) lpc coefficients */ + ); + + void lsf2a( + float *a_coef, /* (o) lpc coefficients */ + float *freq /* (i) lsf coefficients */ + ); + + #endif + +A.40. lsf.c + + /****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + lsf.c + + Copyright (C) The Internet Society (2004). + All Rights Reserved. + + ******************************************************************/ + + #include <string.h> + + + +Andersen, et al. Experimental [Page 172] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + #include <math.h> + + #include "iLBC_define.h" + + /*----------------------------------------------------------------* + * conversion from lpc coefficients to lsf coefficients + *---------------------------------------------------------------*/ + + void a2lsf( + float *freq,/* (o) lsf coefficients */ + float *a /* (i) lpc coefficients */ + ){ + float steps[LSF_NUMBER_OF_STEPS] = + {(float)0.00635, (float)0.003175, (float)0.0015875, + (float)0.00079375}; + float step; + int step_idx; + int lsp_index; + float p[LPC_HALFORDER]; + float q[LPC_HALFORDER]; + float p_pre[LPC_HALFORDER]; + float q_pre[LPC_HALFORDER]; + float old_p, old_q, *old; + float *pq_coef; + float omega, old_omega; + int i; + float hlp, hlp1, hlp2, hlp3, hlp4, hlp5; + + for (i=0; i<LPC_HALFORDER; i++) { + p[i] = (float)-1.0 * (a[i + 1] + a[LPC_FILTERORDER - i]); + q[i] = a[LPC_FILTERORDER - i] - a[i + 1]; + } + + p_pre[0] = (float)-1.0 - p[0]; + p_pre[1] = - p_pre[0] - p[1]; + p_pre[2] = - p_pre[1] - p[2]; + p_pre[3] = - p_pre[2] - p[3]; + p_pre[4] = - p_pre[3] - p[4]; + p_pre[4] = p_pre[4] / 2; + + q_pre[0] = (float)1.0 - q[0]; + q_pre[1] = q_pre[0] - q[1]; + q_pre[2] = q_pre[1] - q[2]; + q_pre[3] = q_pre[2] - q[3]; + q_pre[4] = q_pre[3] - q[4]; + q_pre[4] = q_pre[4] / 2; + + omega = 0.0; + + + +Andersen, et al. Experimental [Page 173] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + old_omega = 0.0; + + old_p = FLOAT_MAX; + old_q = FLOAT_MAX; + + /* Here we loop through lsp_index to find all the + LPC_FILTERORDER roots for omega. */ + + for (lsp_index = 0; lsp_index<LPC_FILTERORDER; lsp_index++) { + + /* Depending on lsp_index being even or odd, we + alternatively solve the roots for the two LSP equations. */ + + + if ((lsp_index & 0x1) == 0) { + pq_coef = p_pre; + old = &old_p; + } else { + pq_coef = q_pre; + old = &old_q; + } + + /* Start with low resolution grid */ + + for (step_idx = 0, step = steps[step_idx]; + step_idx < LSF_NUMBER_OF_STEPS;){ + + /* cos(10piw) + pq(0)cos(8piw) + pq(1)cos(6piw) + + pq(2)cos(4piw) + pq(3)cod(2piw) + pq(4) */ + + hlp = (float)cos(omega * TWO_PI); + hlp1 = (float)2.0 * hlp + pq_coef[0]; + hlp2 = (float)2.0 * hlp * hlp1 - (float)1.0 + + pq_coef[1]; + hlp3 = (float)2.0 * hlp * hlp2 - hlp1 + pq_coef[2]; + hlp4 = (float)2.0 * hlp * hlp3 - hlp2 + pq_coef[3]; + hlp5 = hlp * hlp4 - hlp3 + pq_coef[4]; + + + if (((hlp5 * (*old)) <= 0.0) || (omega >= 0.5)){ + + if (step_idx == (LSF_NUMBER_OF_STEPS - 1)){ + + if (fabs(hlp5) >= fabs(*old)) { + freq[lsp_index] = omega - step; + } else { + freq[lsp_index] = omega; + } + + + +Andersen, et al. Experimental [Page 174] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + + + if ((*old) >= 0.0){ + *old = (float)-1.0 * FLOAT_MAX; + } else { + *old = FLOAT_MAX; + } + + omega = old_omega; + step_idx = 0; + + step_idx = LSF_NUMBER_OF_STEPS; + } else { + + if (step_idx == 0) { + old_omega = omega; + } + + step_idx++; + omega -= steps[step_idx]; + + /* Go back one grid step */ + + step = steps[step_idx]; + } + } else { + + /* increment omega until they are of different sign, + and we know there is at least one root between omega + and old_omega */ + *old = hlp5; + omega += step; + } + } + } + + for (i = 0; i<LPC_FILTERORDER; i++) { + freq[i] = freq[i] * TWO_PI; + } + } + + /*----------------------------------------------------------------* + * conversion from lsf coefficients to lpc coefficients + *---------------------------------------------------------------*/ + + void lsf2a( + float *a_coef, /* (o) lpc coefficients */ + float *freq /* (i) lsf coefficients */ + + + +Andersen, et al. Experimental [Page 175] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + ){ + int i, j; + float hlp; + float p[LPC_HALFORDER], q[LPC_HALFORDER]; + float a[LPC_HALFORDER + 1], a1[LPC_HALFORDER], + a2[LPC_HALFORDER]; + float b[LPC_HALFORDER + 1], b1[LPC_HALFORDER], + b2[LPC_HALFORDER]; + + for (i=0; i<LPC_FILTERORDER; i++) { + freq[i] = freq[i] * PI2; + } + + /* Check input for ill-conditioned cases. This part is not + found in the TIA standard. It involves the following 2 IF + blocks. If "freq" is judged ill-conditioned, then we first + modify freq[0] and freq[LPC_HALFORDER-1] (normally + LPC_HALFORDER = 10 for LPC applications), then we adjust + the other "freq" values slightly */ + + + if ((freq[0] <= 0.0) || (freq[LPC_FILTERORDER - 1] >= 0.5)){ + + + if (freq[0] <= 0.0) { + freq[0] = (float)0.022; + } + + + if (freq[LPC_FILTERORDER - 1] >= 0.5) { + freq[LPC_FILTERORDER - 1] = (float)0.499; + } + + hlp = (freq[LPC_FILTERORDER - 1] - freq[0]) / + (float) (LPC_FILTERORDER - 1); + + for (i=1; i<LPC_FILTERORDER; i++) { + freq[i] = freq[i - 1] + hlp; + } + } + + memset(a1, 0, LPC_HALFORDER*sizeof(float)); + memset(a2, 0, LPC_HALFORDER*sizeof(float)); + memset(b1, 0, LPC_HALFORDER*sizeof(float)); + memset(b2, 0, LPC_HALFORDER*sizeof(float)); + memset(a, 0, (LPC_HALFORDER+1)*sizeof(float)); + memset(b, 0, (LPC_HALFORDER+1)*sizeof(float)); + + + + +Andersen, et al. Experimental [Page 176] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + /* p[i] and q[i] compute cos(2*pi*omega_{2j}) and + cos(2*pi*omega_{2j-1} in eqs. 4.2.2.2-1 and 4.2.2.2-2. + Note that for this code p[i] specifies the coefficients + used in .Q_A(z) while q[i] specifies the coefficients used + in .P_A(z) */ + + for (i=0; i<LPC_HALFORDER; i++) { + p[i] = (float)cos(TWO_PI * freq[2 * i]); + q[i] = (float)cos(TWO_PI * freq[2 * i + 1]); + } + + a[0] = 0.25; + b[0] = 0.25; + + for (i= 0; i<LPC_HALFORDER; i++) { + a[i + 1] = a[i] - 2 * p[i] * a1[i] + a2[i]; + b[i + 1] = b[i] - 2 * q[i] * b1[i] + b2[i]; + a2[i] = a1[i]; + a1[i] = a[i]; + b2[i] = b1[i]; + b1[i] = b[i]; + } + + for (j=0; j<LPC_FILTERORDER; j++) { + + if (j == 0) { + a[0] = 0.25; + b[0] = -0.25; + } else { + a[0] = b[0] = 0.0; + } + + for (i=0; i<LPC_HALFORDER; i++) { + a[i + 1] = a[i] - 2 * p[i] * a1[i] + a2[i]; + b[i + 1] = b[i] - 2 * q[i] * b1[i] + b2[i]; + a2[i] = a1[i]; + a1[i] = a[i]; + b2[i] = b1[i]; + b1[i] = b[i]; + } + + a_coef[j + 1] = 2 * (a[LPC_HALFORDER] + b[LPC_HALFORDER]); + } + + a_coef[0] = 1.0; + } + + + + + +Andersen, et al. Experimental [Page 177] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + +A.41. packing.h + + /****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + packing.h + + Copyright (C) The Internet Society (2004). + All Rights Reserved. + + ******************************************************************/ + + #ifndef __PACKING_H + #define __PACKING_H + + void packsplit( + int *index, /* (i) the value to split */ + int *firstpart, /* (o) the value specified by most + significant bits */ + int *rest, /* (o) the value specified by least + significant bits */ + int bitno_firstpart, /* (i) number of bits in most + significant part */ + int bitno_total /* (i) number of bits in full range + of value */ + ); + + void packcombine( + int *index, /* (i/o) the msb value in the + combined value out */ + int rest, /* (i) the lsb value */ + int bitno_rest /* (i) the number of bits in the + lsb part */ + ); + + void dopack( + unsigned char **bitstream, /* (i/o) on entrance pointer to + place in bitstream to pack + new data, on exit pointer + to place in bitstream to + pack future data */ + int index, /* (i) the value to pack */ + int bitno, /* (i) the number of bits that the + value will fit within */ + int *pos /* (i/o) write position in the + current byte */ + ); + + + +Andersen, et al. Experimental [Page 178] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + void unpack( + unsigned char **bitstream, /* (i/o) on entrance pointer to + place in bitstream to + unpack new data from, on + exit pointer to place in + bitstream to unpack future + data from */ + int *index, /* (o) resulting value */ + int bitno, /* (i) number of bits used to + represent the value */ + int *pos /* (i/o) read position in the + current byte */ + ); + + #endif + +A.42. packing.c + + /****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + packing.c + + Copyright (C) The Internet Society (2004). + All Rights Reserved. + + ******************************************************************/ + + #include <math.h> + #include <stdlib.h> + + #include "iLBC_define.h" + #include "constants.h" + #include "helpfun.h" + #include "string.h" + + /*----------------------------------------------------------------* + * splitting an integer into first most significant bits and + * remaining least significant bits + *---------------------------------------------------------------*/ + + void packsplit( + int *index, /* (i) the value to split */ + int *firstpart, /* (o) the value specified by most + significant bits */ + int *rest, /* (o) the value specified by least + significant bits */ + + + +Andersen, et al. Experimental [Page 179] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + int bitno_firstpart, /* (i) number of bits in most + significant part */ + int bitno_total /* (i) number of bits in full range + of value */ + ){ + int bitno_rest = bitno_total-bitno_firstpart; + + *firstpart = *index>>(bitno_rest); + *rest = *index-(*firstpart<<(bitno_rest)); + } + + /*----------------------------------------------------------------* + * combining a value corresponding to msb's with a value + * corresponding to lsb's + *---------------------------------------------------------------*/ + + void packcombine( + int *index, /* (i/o) the msb value in the + combined value out */ + int rest, /* (i) the lsb value */ + int bitno_rest /* (i) the number of bits in the + lsb part */ + ){ + *index = *index<<bitno_rest; + *index += rest; + } + + /*----------------------------------------------------------------* + * packing of bits into bitstream, i.e., vector of bytes + *---------------------------------------------------------------*/ + + void dopack( + unsigned char **bitstream, /* (i/o) on entrance pointer to + place in bitstream to pack + new data, on exit pointer + to place in bitstream to + pack future data */ + int index, /* (i) the value to pack */ + int bitno, /* (i) the number of bits that the + value will fit within */ + int *pos /* (i/o) write position in the + current byte */ + ){ + int posLeft; + + /* Clear the bits before starting in a new byte */ + + if ((*pos)==0) { + + + +Andersen, et al. Experimental [Page 180] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + **bitstream=0; + } + + while (bitno>0) { + + /* Jump to the next byte if end of this byte is reached*/ + + if (*pos==8) { + *pos=0; + (*bitstream)++; + **bitstream=0; + } + + posLeft=8-(*pos); + + /* Insert index into the bitstream */ + + if (bitno <= posLeft) { + **bitstream |= (unsigned char)(index<<(posLeft-bitno)); + *pos+=bitno; + bitno=0; + } else { + **bitstream |= (unsigned char)(index>>(bitno-posLeft)); + + *pos=8; + index-=((index>>(bitno-posLeft))<<(bitno-posLeft)); + + bitno-=posLeft; + } + } + } + + /*----------------------------------------------------------------* + * unpacking of bits from bitstream, i.e., vector of bytes + *---------------------------------------------------------------*/ + + void unpack( + unsigned char **bitstream, /* (i/o) on entrance pointer to + place in bitstream to + unpack new data from, on + exit pointer to place in + bitstream to unpack future + data from */ + int *index, /* (o) resulting value */ + int bitno, /* (i) number of bits used to + represent the value */ + int *pos /* (i/o) read position in the + current byte */ + + + +Andersen, et al. Experimental [Page 181] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + ){ + int BitsLeft; + + *index=0; + + while (bitno>0) { + + /* move forward in bitstream when the end of the + byte is reached */ + + if (*pos==8) { + *pos=0; + (*bitstream)++; + } + + BitsLeft=8-(*pos); + + /* Extract bits to index */ + + if (BitsLeft>=bitno) { + *index+=((((**bitstream)<<(*pos)) & 0xFF)>>(8-bitno)); + + *pos+=bitno; + bitno=0; + } else { + + if ((8-bitno)>0) { + *index+=((((**bitstream)<<(*pos)) & 0xFF)>> + (8-bitno)); + *pos=8; + } else { + *index+=(((int)(((**bitstream)<<(*pos)) & 0xFF))<< + (bitno-8)); + *pos=8; + } + bitno-=BitsLeft; + } + } + } + +A.43. StateConstructW.h + + /****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + StateConstructW.h + + + + +Andersen, et al. Experimental [Page 182] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + Copyright (C) The Internet Society (2004). + All Rights Reserved. + + ******************************************************************/ + + #ifndef __iLBC_STATECONSTRUCTW_H + #define __iLBC_STATECONSTRUCTW_H + + void StateConstructW( + int idxForMax, /* (i) 6-bit index for the quantization of + max amplitude */ + int *idxVec, /* (i) vector of quantization indexes */ + float *syntDenum, /* (i) synthesis filter denumerator */ + float *out, /* (o) the decoded state vector */ + int len /* (i) length of a state vector */ + ); + + #endif + +A.44. StateConstructW.c + + /****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + StateConstructW.c + + Copyright (C) The Internet Society (2004). + All Rights Reserved. + + ******************************************************************/ + + #include <math.h> + #include <string.h> + + #include "iLBC_define.h" + #include "constants.h" + #include "filter.h" + + /*----------------------------------------------------------------* + * decoding of the start state + *---------------------------------------------------------------*/ + + void StateConstructW( + int idxForMax, /* (i) 6-bit index for the quantization of + max amplitude */ + int *idxVec, /* (i) vector of quantization indexes */ + float *syntDenum, /* (i) synthesis filter denumerator */ + + + +Andersen, et al. Experimental [Page 183] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + float *out, /* (o) the decoded state vector */ + int len /* (i) length of a state vector */ + ){ + float maxVal, tmpbuf[LPC_FILTERORDER+2*STATE_LEN], *tmp, + numerator[LPC_FILTERORDER+1]; + float foutbuf[LPC_FILTERORDER+2*STATE_LEN], *fout; + int k,tmpi; + + /* decoding of the maximum value */ + + maxVal = state_frgqTbl[idxForMax]; + maxVal = (float)pow(10,maxVal)/(float)4.5; + + /* initialization of buffers and coefficients */ + + memset(tmpbuf, 0, LPC_FILTERORDER*sizeof(float)); + memset(foutbuf, 0, LPC_FILTERORDER*sizeof(float)); + for (k=0; k<LPC_FILTERORDER; k++) { + numerator[k]=syntDenum[LPC_FILTERORDER-k]; + } + numerator[LPC_FILTERORDER]=syntDenum[0]; + tmp = &tmpbuf[LPC_FILTERORDER]; + fout = &foutbuf[LPC_FILTERORDER]; + + /* decoding of the sample values */ + + for (k=0; k<len; k++) { + tmpi = len-1-k; + /* maxVal = 1/scal */ + tmp[k] = maxVal*state_sq3Tbl[idxVec[tmpi]]; + } + + /* circular convolution with all-pass filter */ + + memset(tmp+len, 0, len*sizeof(float)); + ZeroPoleFilter(tmp, numerator, syntDenum, 2*len, + LPC_FILTERORDER, fout); + for (k=0;k<len;k++) { + out[k] = fout[len-1-k]+fout[2*len-1-k]; + } + } + + + + + + + + + + +Andersen, et al. Experimental [Page 184] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + +A.45. StateSearchW.h + + /****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + StateSearchW.h + + Copyright (C) The Internet Society (2004). + All Rights Reserved. + + ******************************************************************/ + + #ifndef __iLBC_STATESEARCHW_H + #define __iLBC_STATESEARCHW_H + + void AbsQuantW( + iLBC_Enc_Inst_t *iLBCenc_inst, + /* (i) Encoder instance */ + float *in, /* (i) vector to encode */ + float *syntDenum, /* (i) denominator of synthesis filter */ + float *weightDenum, /* (i) denominator of weighting filter */ + int *out, /* (o) vector of quantizer indexes */ + int len, /* (i) length of vector to encode and + vector of quantizer indexes */ + int state_first /* (i) position of start state in the + 80 vec */ + ); + + void StateSearchW( + iLBC_Enc_Inst_t *iLBCenc_inst, + /* (i) Encoder instance */ + float *residual,/* (i) target residual vector */ + float *syntDenum, /* (i) lpc synthesis filter */ + float *weightDenum, /* (i) weighting filter denuminator */ + int *idxForMax, /* (o) quantizer index for maximum + amplitude */ + int *idxVec, /* (o) vector of quantization indexes */ + int len, /* (i) length of all vectors */ + int state_first /* (i) position of start state in the + 80 vec */ + ); + + + #endif + + + + + + +Andersen, et al. Experimental [Page 185] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + +A.46. StateSearchW.c + + /****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + StateSearchW.c + + Copyright (C) The Internet Society (2004). + All Rights Reserved. + + ******************************************************************/ + + #include <math.h> + #include <string.h> + + #include "iLBC_define.h" + #include "constants.h" + #include "filter.h" + #include "helpfun.h" + + /*----------------------------------------------------------------* + * predictive noise shaping encoding of scaled start state + * (subrutine for StateSearchW) + *---------------------------------------------------------------*/ + + void AbsQuantW( + iLBC_Enc_Inst_t *iLBCenc_inst, + /* (i) Encoder instance */ + float *in, /* (i) vector to encode */ + float *syntDenum, /* (i) denominator of synthesis filter */ + float *weightDenum, /* (i) denominator of weighting filter */ + int *out, /* (o) vector of quantizer indexes */ + int len, /* (i) length of vector to encode and + vector of quantizer indexes */ + int state_first /* (i) position of start state in the + 80 vec */ + ){ + float *syntOut; + float syntOutBuf[LPC_FILTERORDER+STATE_SHORT_LEN_30MS]; + float toQ, xq; + int n; + int index; + + /* initialization of buffer for filtering */ + + memset(syntOutBuf, 0, LPC_FILTERORDER*sizeof(float)); + + + + +Andersen, et al. Experimental [Page 186] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + /* initialization of pointer for filtering */ + + syntOut = &syntOutBuf[LPC_FILTERORDER]; + + /* synthesis and weighting filters on input */ + + if (state_first) { + AllPoleFilter (in, weightDenum, SUBL, LPC_FILTERORDER); + } else { + AllPoleFilter (in, weightDenum, + iLBCenc_inst->state_short_len-SUBL, + LPC_FILTERORDER); + } + + /* encoding loop */ + + for (n=0; n<len; n++) { + + /* time update of filter coefficients */ + + if ((state_first)&&(n==SUBL)){ + syntDenum += (LPC_FILTERORDER+1); + weightDenum += (LPC_FILTERORDER+1); + + /* synthesis and weighting filters on input */ + AllPoleFilter (&in[n], weightDenum, len-n, + LPC_FILTERORDER); + + } else if ((state_first==0)&& + (n==(iLBCenc_inst->state_short_len-SUBL))) { + syntDenum += (LPC_FILTERORDER+1); + weightDenum += (LPC_FILTERORDER+1); + + /* synthesis and weighting filters on input */ + AllPoleFilter (&in[n], weightDenum, len-n, + LPC_FILTERORDER); + + } + + /* prediction of synthesized and weighted input */ + + syntOut[n] = 0.0; + AllPoleFilter (&syntOut[n], weightDenum, 1, + LPC_FILTERORDER); + + /* quantization */ + + toQ = in[n]-syntOut[n]; + + + +Andersen, et al. Experimental [Page 187] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + sort_sq(&xq, &index, toQ, state_sq3Tbl, 8); + out[n]=index; + syntOut[n] = state_sq3Tbl[out[n]]; + + /* update of the prediction filter */ + + AllPoleFilter(&syntOut[n], weightDenum, 1, + LPC_FILTERORDER); + } + } + + /*----------------------------------------------------------------* + * encoding of start state + *---------------------------------------------------------------*/ + + void StateSearchW( + iLBC_Enc_Inst_t *iLBCenc_inst, + /* (i) Encoder instance */ + float *residual,/* (i) target residual vector */ + float *syntDenum, /* (i) lpc synthesis filter */ + float *weightDenum, /* (i) weighting filter denuminator */ + int *idxForMax, /* (o) quantizer index for maximum + amplitude */ + int *idxVec, /* (o) vector of quantization indexes */ + int len, /* (i) length of all vectors */ + int state_first /* (i) position of start state in the + 80 vec */ + ){ + float dtmp, maxVal; + float tmpbuf[LPC_FILTERORDER+2*STATE_SHORT_LEN_30MS]; + float *tmp, numerator[1+LPC_FILTERORDER]; + float foutbuf[LPC_FILTERORDER+2*STATE_SHORT_LEN_30MS], *fout; + int k; + float qmax, scal; + + /* initialization of buffers and filter coefficients */ + + memset(tmpbuf, 0, LPC_FILTERORDER*sizeof(float)); + memset(foutbuf, 0, LPC_FILTERORDER*sizeof(float)); + for (k=0; k<LPC_FILTERORDER; k++) { + numerator[k]=syntDenum[LPC_FILTERORDER-k]; + } + numerator[LPC_FILTERORDER]=syntDenum[0]; + tmp = &tmpbuf[LPC_FILTERORDER]; + fout = &foutbuf[LPC_FILTERORDER]; + + /* circular convolution with the all-pass filter */ + + + + +Andersen, et al. Experimental [Page 188] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + memcpy(tmp, residual, len*sizeof(float)); + memset(tmp+len, 0, len*sizeof(float)); + ZeroPoleFilter(tmp, numerator, syntDenum, 2*len, + LPC_FILTERORDER, fout); + for (k=0; k<len; k++) { + fout[k] += fout[k+len]; + } + + /* identification of the maximum amplitude value */ + + maxVal = fout[0]; + for (k=1; k<len; k++) { + + if (fout[k]*fout[k] > maxVal*maxVal){ + maxVal = fout[k]; + } + } + maxVal=(float)fabs(maxVal); + + /* encoding of the maximum amplitude value */ + + if (maxVal < 10.0) { + maxVal = 10.0; + } + maxVal = (float)log10(maxVal); + sort_sq(&dtmp, idxForMax, maxVal, state_frgqTbl, 64); + + /* decoding of the maximum amplitude representation value, + and corresponding scaling of start state */ + + maxVal=state_frgqTbl[*idxForMax]; + qmax = (float)pow(10,maxVal); + scal = (float)(4.5)/qmax; + for (k=0; k<len; k++){ + fout[k] *= scal; + } + + /* predictive noise shaping encoding of scaled start state */ + + AbsQuantW(iLBCenc_inst, fout,syntDenum, + weightDenum,idxVec, len, state_first); + } + + + + + + + + + +Andersen, et al. Experimental [Page 189] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + +A.47. syntFilter.h + + /****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + syntFilter.h + + Copyright (C) The Internet Society (2004). + All Rights Reserved. + + ******************************************************************/ + + #ifndef __iLBC_SYNTFILTER_H + #define __iLBC_SYNTFILTER_H + + void syntFilter( + float *Out, /* (i/o) Signal to be filtered */ + float *a, /* (i) LP parameters */ + int len, /* (i) Length of signal */ + float *mem /* (i/o) Filter state */ + ); + + #endif + +A.48. syntFilter.c + + /****************************************************************** + + iLBC Speech Coder ANSI-C Source Code + + syntFilter.c + + Copyright (C) The Internet Society (2004). + All Rights Reserved. + + ******************************************************************/ + + #include "iLBC_define.h" + + /*----------------------------------------------------------------* + * LP synthesis filter. + *---------------------------------------------------------------*/ + + void syntFilter( + float *Out, /* (i/o) Signal to be filtered */ + float *a, /* (i) LP parameters */ + int len, /* (i) Length of signal */ + + + +Andersen, et al. Experimental [Page 190] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + float *mem /* (i/o) Filter state */ + ){ + int i, j; + float *po, *pi, *pa, *pm; + + po=Out; + + /* Filter first part using memory from past */ + + for (i=0; i<LPC_FILTERORDER; i++) { + pi=&Out[i-1]; + pa=&a[1]; + pm=&mem[LPC_FILTERORDER-1]; + for (j=1; j<=i; j++) { + *po-=(*pa++)*(*pi--); + } + for (j=i+1; j<LPC_FILTERORDER+1; j++) { + *po-=(*pa++)*(*pm--); + } + po++; + } + + /* Filter last part where the state is entirely in + the output vector */ + + for (i=LPC_FILTERORDER; i<len; i++) { + pi=&Out[i-1]; + pa=&a[1]; + for (j=1; j<LPC_FILTERORDER+1; j++) { + *po-=(*pa++)*(*pi--); + } + po++; + } + + /* Update state vector */ + + memcpy(mem, &Out[len-LPC_FILTERORDER], + LPC_FILTERORDER*sizeof(float)); + } + + + + + + + + + + + + +Andersen, et al. Experimental [Page 191] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + +Authors' Addresses + + Soren Vang Andersen + Department of Communication Technology + Aalborg University + Fredrik Bajers Vej 7A + 9200 Aalborg + Denmark + + Phone: ++45 9 6358627 + EMail: sva@kom.auc.dk + + + Alan Duric + Telio AS + Stoperigt. 2 + Oslo, N-0250 + Norway + + Phone: +47 21673555 + EMail: alan.duric@telio.no + + + Henrik Astrom + Global IP Sound AB + Olandsgatan 42 + Stockholm, S-11663 + Sweden + + Phone: +46 8 54553040 + EMail: henrik.astrom@globalipsound.com + + + Roar Hagen + Global IP Sound AB + Olandsgatan 42 + Stockholm, S-11663 + Sweden + + Phone: +46 8 54553040 + EMail: roar.hagen@globalipsound.com + + + + + + + + + + +Andersen, et al. Experimental [Page 192] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + + W. Bastiaan Kleijn + Global IP Sound AB + Olandsgatan 42 + Stockholm, S-11663 + Sweden + + Phone: +46 8 54553040 + EMail: bastiaan.kleijn@globalipsound.com + + + Jan Linden + Global IP Sound Inc. + 900 Kearny Street, suite 500 + San Francisco, CA-94133 + USA + + Phone: +1 415 397 2555 + EMail: jan.linden@globalipsound.com + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +Andersen, et al. Experimental [Page 193] + +RFC 3951 Internet Low Bit Rate Codec December 2004 + + +Full Copyright Statement + + Copyright (C) The Internet Society (2004). + + This document is subject to the rights, licenses and restrictions + contained in BCP 78, and except as set forth therein, the authors + retain all their rights. + + This document and the information contained herein are provided on an + "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS + OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET + ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, + INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE + INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED + WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. + +Intellectual Property + + The IETF takes no position regarding the validity or scope of any + Intellectual Property Rights or other rights that might be claimed to + pertain to the implementation or use of the technology described in + this document or the extent to which any license under such rights + might or might not be available; nor does it represent that it has + made any independent effort to identify any such rights. Information + on the IETF's procedures with respect to rights in IETF Documents can + be found in BCP 78 and BCP 79. + + Copies of IPR disclosures made to the IETF Secretariat and any + assurances of licenses to be made available, or the result of an + attempt made to obtain a general license or permission for the use of + such proprietary rights by implementers or users of this + specification can be obtained from the IETF on-line IPR repository at + http://www.ietf.org/ipr. + + The IETF invites any interested party to bring to its attention any + copyrights, patents or patent applications, or other proprietary + rights that may cover technology that may be required to implement + this standard. Please address the information to the IETF at ietf- + ipr@ietf.org. + + +Acknowledgement + + Funding for the RFC Editor function is currently provided by the + Internet Society. + + + + + + +Andersen, et al. Experimental [Page 194] + |