From 4bfd864f10b68b71482b35c818559068ef8d5797 Mon Sep 17 00:00:00 2001 From: Thomas Voss Date: Wed, 27 Nov 2024 20:54:24 +0100 Subject: doc: Add RFC documents --- doc/rfc/rfc2029.txt | 339 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 339 insertions(+) create mode 100644 doc/rfc/rfc2029.txt (limited to 'doc/rfc/rfc2029.txt') diff --git a/doc/rfc/rfc2029.txt b/doc/rfc/rfc2029.txt new file mode 100644 index 0000000..088462e --- /dev/null +++ b/doc/rfc/rfc2029.txt @@ -0,0 +1,339 @@ + + + + + + +Network Working Group M. Speer +Request for Comment: 2029 D. Hoffman +Category: Standards Track Sun Microsystems, Inc. + October 1996 + + + RTP Payload Format of Sun's CellB Video Encoding + +Status of this Memo + + This document specifies an Internet standards track protocol for the + Internet community, and requests discussion and suggestions for + improvements. Please refer to the current edition of the "Internet + Official Protocol Standards" (STD 1) for the standardization state + and status of this protocol. Distribution of this memo is unlimited. + +Abstract + + This memo describes a packetization scheme for the CellB video + encoding. The scheme proposed allows applications to transport CellB + video flows over protocols used by RTP. This document is meant for + implementors of video applications that want to use RTP and CellB. + +1. Introduction + + The Cell image compression algorithm is a variable bit-rate video + coding scheme. It provides "high" quality, low bit-rate image + compression at low computational cost. The bytestream that is + produced by the Cell encoder consists of instructional codes and + information about the compressed image. + + For futher information on Cell compression technology, refer to [1]. + Currently, there are two versions of the Cell compression technology: + CellA and CellB. CellA is primarily designed for the encoding of + stored video intended for local display, and will not be discussed in + this memo. + + CellB, derived from CellA, has been optimized for network-based video + applications. It is computationally symmetric in both encode and + decode. CellB utilizes a fixed colormap and vector quantization + techniques in the YUV color space to achieve compression. + + + + + + + + + + +Speer & Hoffman Standards Track [Page 1] + +RFC 2029 RTP Payload Format October 1996 + + +2. Network Packetization and Encapsulation + +2.1 RTP Usage + + The RTP timestamp is in units of 90KHz. The same timestamp value is + used for all packet payloads of a frame. The RTP maker bit denotes + the end of a frame. + +2.2 CellB Header + + The packetization of the CellB bytestream is designed to make the + resulting packet stream robust to packet loss. To achieve this goal, + an additional header is added to each RTP packet to uniquely identify + the location of the first cell of the packet within the current + frame. In addition, the width and height of the frame in pixels is + carried in each CellB packet header. Although the size can only + change between frames, it is carried in every packet to simplify the + packet encoding. + + 0 1 2 3 + 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Cell X Location | Cell Y Location | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Width of Image | Height of Image | + +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ + | Compressed CellB Data | + | .... | + +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ + + All fields are 16-bit unsigned integers in network byte order, and + are placed at the beginning of the payload for each RTP packet. The + Cell X and the Cell Y Location coordinates are expressed as cell + coordinates, not pixel coordinates. Since cells represent 4x4 blocks + of pixels, the X or Y dimension of the cell coordinates range in + value from 0 through 1/4 of the of the same dimension in pixel + coordinates. + +2.3 Packetization Rules + + A packet can be of any size chosen by the implementor, up to a full + frame. All multi-byte codes must be completely contained within a + packet. In general, the implementor should avoid packet sizes that + result in fragmentation by the network. + + + + + + + +Speer & Hoffman Standards Track [Page 2] + +RFC 2029 RTP Payload Format October 1996 + + +3. References + + 1. "Cell Image Compression Byte Stream Description," + ftp://playground.sun.com:/pub/multimedia/video/ + cellbytestream.ps.Z + + 2. Turletti, T., and C. Huitema, "RTP Payload Format + for H.261 Video Streams", RFC 2032, October 1996. + + 3. Schulzrinne, H., Casner, S., Frederick, R., and + V. Jacobson, "RTP: A Transport Protocol for Real-Time + Applications", RFC 1889, January 1996. + + 4. Schulzrinne, H., "RTP Profile for Audio and Video + Conferences with Minimal Control", RFC 1890, + January 1996. + +4 Authors' Addresses + + Michael F. Speer + Sun Microsystems Computer Corporation + 2550 Garcia Ave MailStop UMPK14-305 + Mountain View, CA 94043 + + Voice: +1 415 786 6368 + Fax: +1 415 786 6445 + EMail: michael.speer@eng.sun.com + + + Don Hoffman + Sun Microsystems Computer Corporation + 2550 Garcia Ave MailStop UMPK14-305 + Mountain View, CA 94043 + + Voice: +1 415 786 6370 + Fax: +1 415 786 6445 + EMail: don.hoffman@eng.sun.com + + + + + + + + + + + + + + +Speer & Hoffman Standards Track [Page 3] + +RFC 2029 RTP Payload Format October 1996 + + +Appendix A - Structure of the CellB Video Stream + + The CellB bytestream consists of cell codes, skip codes and + quantization-table specific codes. These are now described. + +A.1 CellB Cell Code + + Cell codes are 4 bytes in length, and describe a 4x4 pixel cell. + There are two possible luminance (Y) levels for each cell, but only + one pair of chrominance (UV) values. The CellB cell code is shown + below: + + + 0 1 2 3 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + |0 M M M M M M M M M M M M M M M|U V U V U V U V|Y Y Y Y Y Y Y Y| + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + 4x4 Bitmask U/V Code Y/Y Code + + The first two bytes of the cell code are a bitmask. Each bit in the + mask represents a pixel in a 16-pixel cell. Bit 0 represents the + value of the upper right-hand pixel of the cell, and subsequent bits + represent the pixels in row-major order. If a pixel's bit is set in + the 4x4 Bitmask, then the pixel will be rendered with the pixel value + . If the pixel's bit is not set in the bitmask, then the + pixel's value will be rendered with the value . The + bitmask for the cell is normalized so that the most significant bit + is always 0 (i.e., corresponding to ). + + The U/V field of the cell code represents the chrominance component. + This code is in index into a table of vectors that represents two + independent components of chrominance. + + The Y/Y field of the cell code represents two luminance values (Y(0) + and Y(1)). This code is an index into a table of two-compoment + luminance vectors. + + The derivation of the U/V and Y/Y tables is outside the scope of this + memo. A complete discussion can be found in [1]. + + + + + + + + + + + +Speer & Hoffman Standards Track [Page 4] + +RFC 2029 RTP Payload Format October 1996 + + +A.2 CellB Skip Code + + The single byte CellB skip code tells the CellB decoder to skip the + next S+1 cells in the current video frame being decoded. The maximum + number of cells that can be skipped is 32. The format of the skip + code is shown below. + + 0 1 2 3 4 5 6 7 + +-+-+-+-+-+-+-+-+ + |1 0 0 S S S S S| + +-+-+-+-+-+-+-+-+ + +A.3 CellB Y/Y Table Code + + The single byte "new Y/Y table" code is used to tell the decoder that + the next 512 bytes are a new Y/Y quantization table. The code and + the representation of the table are shown below. The sample + encoder/decoder pair in this document do not implement this feature + of the CellB compression. However, future CellB codecs may implement + this feature. + + 0 1 2 3 4 5 6 7 + +-+-+-+-+-+-+-+-+ + |1 1 1 1 1 1 1 0| + +-+-+-+-+-+-+-+-+ + + The format of the new Y/Y table is: + + 0 1 2 3 + 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Y1_000 | Y2_000 | Y1_001 | Y2_001 | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + . + . + . + + 0 1 2 3 + 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Y1_254 | Y2_254 | Y1_255 | Y2_255 | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + + + + + + + +Speer & Hoffman Standards Track [Page 5] + +RFC 2029 RTP Payload Format October 1996 + + +A.4 CellB U/V Table Code + + The single byte "new U/V table" code is used to tell the decoder that + the next 512 bytes represent a new U/V quantization table. The code + is shown below. The sample encoder/decoder pair provided in this + document do not implement this feature of the CellB compression. + However, future CellB codecs may implement this feature. + + 0 1 2 3 4 5 6 7 + +-+-+-+-+-+-+-+-+ + |1 1 1 1 1 1 1 1| + +-+-+-+-+-+-+-+-+ + + The bytes of the new U/V quantization table are arranged as: + + 0 1 2 3 + 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | U_000 | V_000 | U_001 | V_001 | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + . + . + . + + 0 1 2 3 + 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | U_254 | V_254 | U_255 | V_255 | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + +Appendix B - Availability of CellB + + It is the viewpoint of Sun Microsystems, Inc, that CellB is + publically available for use without any license. + + + + + + + + + + + + + + + + +Speer & Hoffman Standards Track [Page 6] + -- cgit v1.2.3