path: root/doc/rfc/rfc3189.txt

Network Working Group                                       K. Kobayashi
Request for Comments: 3189             Communication Research Laboratory
Category: Standards Track                                       A. Ogawa
                                                         Keio University
                                                               S. Casner
                                                           Packet Design
                                                              C. Bormann
                                                 Universitaet Bremen TZI
                                                            January 2002


              RTP Payload Format for DV (IEC 61834) Video

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.

Copyright Notice

   Copyright (C) The Internet Society (2002).  All Rights Reserved.

Abstract

   This document specifies the packetization scheme for encapsulating
   the compressed digital video data streams commonly known as "DV" into
   a payload format for the Real-Time Transport Protocol (RTP).

1. Introduction

   This document specifies payload formats for encapsulating both
   consumer- and professional-use DV format data streams into the Real-
   time Transport Protocol (RTP), version 2 [6].  DV compression audio
   and video formats were designed for helical-scan magnetic tape media.
   The DV standards for consumer-market devices, the IEC 61883 and 61834
   series, cover many aspects of consumer-use digital video, including
   mechanical specifications of a cassette, magnetic recording format,
   error correction on the magnetic tape, DCT video encoding format, and
   audio encoding format [1].  The digital interface part of IEC 61883
   defines an interface on an IEEE 1394 network [2,3].  This
   specification set supports several video formats: SD-VCR (Standard
   Definition), HD-VCR (High Definition), SDL-VCR (Standard Definition -
   Long), PALPlus, DVB (Digital Video Broadcast) and ATV (Advanced
   Television).  North American formats are indicated with a number of
   lines and "/60", while European formats use "/50".  DV standards



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RFC 3189      RTP Payload Format for DV (IEC 61834) Video   January 2002


   extended for professional use were published by SMPTE as 306M and
   314M, for different sampling systems, higher color resolution, and
   faster bit rates [4,5].

   There are two kinds of DV, one for consumer use and the other for
   professional.  The original "DV" specification designed for
   consumer-use digital VCRs is approved as the IEC 61834 standard set.
   The specifications for professional DV are published as SMPTE 306M
   and 314M.  Both encoding formats are based on consumer DV and used in
   SMPTE D-7 and D-9 video systems.  The RTP payload format specified in
   this document supports IEC 61834 consumer DV and professional SMPTE
   306M and 314M (DV-Based) formats.

   IEC 61834 also includes magnetic tape recording for digital TV
   broadcasting systems (such as DVB and ATV) that use MPEG2 encoding.
   The payload format for encapsulating MPEG2 into RTP has already been
   defined in RFC 2250 [7] and others.

   Consequently, the payload specified in this document will support six
   video formats of the IEC standard: SD-VCR (525/60, 625/50), HD-VCR
   (1125/60, 1250/50) and SDL-VCR (525/60, 625/50), and six of the SMPTE
   standards: 306M (525/60, 625/50), 314M 25Mbps (525/60, 625/50) and
   314M 50Mbps (525/60, 625/50).  In the future it can be extended into
   other high-definition formats.

   Throughout this specification, we make extensive use of the
   terminology of IEC and SMPTE standards.  The reader should consult
   the original references for definitions of these terms.

1.1 Terminology

   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 RFC 2119 [8].

2. DV format encoding

   The DV format only uses the DCT compression technique within each
   frame, contrasted with the interframe compression of the MPEG video
   standards [9,10].  All video data, including audio and other system
   data, are managed within the picture frame unit of video.

   The DV video encoding is composed of a three-level hierarchical
   structure.  A picture frame is divided into rectangle- or clipped-
   rectangle-shaped DCT super blocks.  DCT super blocks are divided into
   27 rectangle- or square-shaped DCT macro blocks.





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RFC 3189      RTP Payload Format for DV (IEC 61834) Video   January 2002


   Audio data is encoded with PCM format.  The sampling frequency is 32
   kHz, 44.1 kHz or 48 kHz and the quantization is 12-bit non-linear,
   16-bit linear or 20-bit linear.  The number of channels may be up to
   8.  Only certain combinations of these parameters are allowed
   depending upon the video format; the restrictions are specified in
   each document.

   A frame of data in the DV format stream is divided into several "DIF
   sequences".  A DIF sequence is composed of an integral number of 80-
   byte DIF blocks.  A DIF block is the primitive unit for all treatment
   of DV streams.  Each DIF block contains a 3-byte ID header that
   specifies the type of the DIF block and its position in the DIF
   sequence.  Five types of DIF blocks are defined: DIF sequence header,
   Subcode, Video Auxiliary information (VAUX), Audio, and Video.  Audio
   DIF blocks are composed of 5 bytes of Audio Auxiliary data (AAUX) and
   72 bytes of audio data.

   Each RTP packet starts with the RTP header as defined in RFC 1889
   [6].  No additional payload-format-specific header is required for
   this payload format.

2.1 RTP header usage

   The RTP header fields that have a meaning specific to the DV format
   are described as follows:

   Payload type (PT): The payload type is dynamically assigned by means
   outside the scope of this document.  If multiple DV encoding formats
   are to be used within one RTP session, then multiple dynamic payload
   types MUST be assigned, one for each DV encoding format.  The sender
   MUST change to the corresponding payload type whenever the encoding
   format is changed.

   Timestamp: 32-bit 90 kHz timestamp representing the time at which the
   first data in the frame was sampled.  All RTP packets within the same
   video frame MUST have the same timestamp.  The timestamp SHOULD
   increment by a multiple of the nominal interval for one frame time,
   as given in the following table:

       Mode        Frame rate (Hz)      Increase of one frame
                                        in 90kHz timestamp

      525-60         29.97                   3003
      625-50         25                      3600
      1125-60        30                      3000
      1250-50        25                      3600





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RFC 3189      RTP Payload Format for DV (IEC 61834) Video   January 2002


   When the DV stream is obtained from an IEEE 1394 interface, the
   progress of video frame times MAY be monitored using the SYT
   timestamp carried in the CIP header as specified in IEC 61883 [2].

   Marker bit (M): The marker bit of the RTP fixed header is set to one
   on the last packet of a video frame, and otherwise, must be zero.
   The M bit allows the receiver to know that it has received the last
   packet of a frame so it can display the image without waiting for the
   first packet of the next frame to arrive to detect the frame change.
   However, detection of a frame change MUST NOT rely on the marker bit
   since the last packet of the frame might be lost.  Detection of a
   frame change MUST be based on a difference in the RTP timestamp.

2.2 DV data encapsulation into RTP payload

   Integral DIF blocks are placed into the RTP payload beginning
   immediately after the RTP header.  Any number of DIF blocks may be
   packed into one RTP packet, except that all DIF blocks in one RTP
   packet must be from the same video frame.  DIF blocks from the next
   video frame MUST NOT be packed into the same RTP packet even if more
   payload space remains.  This requirement stems from the fact that the
   transition from one video frame to the next is indicated by a change
   in the RTP timestamp.  It also reduces the processing complexity on
   the receiver.  Since the RTP payload contains an integral number of
   DIF blocks, the length of the RTP payload will be a multiple of 80
   bytes.

   Audio and video data may be transmitted as one bundled RTP stream or
   in separate RTP streams (unbundled).  The choice MUST be indicated as
   part of the assignment of the dynamic payload type and MUST remain
   unchanged for the duration of the RTP session to avoid complicated
   procedures of sequence number synchronization.  The RTP sender MAY
   omit DIF-sequence header and subcode DIF blocks from a stream since
   the information is either known out-of-band or may not be required
   for RTP transport.  When sending DIF-sequence header and subcode DIF
   blocks, both types of blocks MUST be included in the video stream.

   DV streams include "source" and "source control" packs that carry
   information indispensable for proper decoding, such as aspect ratio,
   picture position, quantization of audio sampling, number of audio
   channels, audio channel assignment, and language of the audio.
   However, describing all of these attributes with a signaling protocol
   would require large descriptions to enumerate all the combinations.
   Therefore, no Session Description Protocol (SDP) [13] parameters for
   these attributes are defined in this document.  Instead, the RTP
   sender MUST transmit at least those VAUX DIF blocks and/or audio DIF
   blocks with AAUX information bytes that include "source" and "source
   control" packs containing the indispensable information for decoding.



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RFC 3189      RTP Payload Format for DV (IEC 61834) Video   January 2002


   In the case of one bundled stream, DIF blocks for both audio and
   video are packed into RTP packets in the same order as they were
   encoded.

   In the case of an unbundled stream, only the header, subcode, video
   and VAUX DIF blocks are sent within the video stream.  Audio is sent
   in a different stream if desired, using a different RTP payload type.
   It is also possible to send audio duplicated in a separate stream, in
   addition to bundling it in with the video stream.

   When using unbundled mode, it is RECOMMENDED that the audio stream
   data be extracted from the DIF blocks and repackaged into the
   corresponding RTP payload format for the audio encoding (DAT12, L16,
   L20) [11,12] in order to maximize interoperability with non-DV-
   capable receivers while maintaining the original source quality.

   In the case of unbundled transmission where both audio and video are
   sent in the DV format, the same timestamp SHOULD be used for both
   audio and video data within the same frame to simplify the lip
   synchronization effort on the receiver.  Lip synchronization may also
   be achieved using reference timestamps passed in RTCP as described in
   RFC 1889 [6].

   The sender MAY reduce the video frame rate by discarding the video
   data and VAUX DIF blocks for some of the video frames.  The RTP
   timestamp must still be incremented to account for the discarded
   frames.  The sender MAY alternatively reduce bandwidth by discarding
   video data DIF blocks for portions of the image which are unchanged
   from the previous image.  To enable this bandwidth reduction,
   receivers SHOULD implement an error concealment strategy to
   accommodate lost or missing DIF blocks, e.g., repeating the
   corresponding DIF block from the previous image.

3. SDP Signaling for RTP/DV

   When using SDP (Session Description Protocol) [13] for negotiation of
   the RTP payload information, the format described in this document
   SHOULD be used.  SDP descriptions will be slightly different for a
   bundled stream and an unbundled stream.

   When a DV stream is sent to port 31394 using RTP payload type
   identifier 111, the m=?? line will be like:

      m=video 31394 RTP/AVP 111

   The a=rtpmap attribute will be like:

      a=rtpmap:111 DV/90000



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RFC 3189      RTP Payload Format for DV (IEC 61834) Video   January 2002


   "DV" is the encoding name for the DV video payload format defined in
   this document.  The "90000" specifies the RTP timestamp clock rate,
   which for the payload format defined in this document is a 90kHz
   clock.

   In SDP, format-specific parameters are defined as a=fmtp, as below:

      a=fmtp:<format> <format-specific parameters>

   In the DV video payload format, the a=fmtp line will be used to show
   the encoding type within the DV video and will be used as below:

      a=fmtp:<payload type> encode=<DV-video encoding>

   The required parameter <DV-video encoding> specifies which type of DV
   format is used.  The DV format name will be one of the following:

      SD-VCR/525-60
      SD-VCR/625-50
      HD-VCR/1125-60
      HD-VCR/1250-50
      SDL-VCR/525-60
      SDL-VCR/625-50
      306M/525-60
      306M/625-50
      314M-25/525-60
      314M-25/625-50
      314M-50/525-60
      314M-50/625-50

   In order to show whether the audio data is bundled into the DV stream
   or not, a format specific parameter is defined as below:

      a=fmtp:<payload type> audio=<audio bundled>

   The optional parameter <audio bundled> will be one of the following:

      bundled
      none     (default)

   If the fmtp audio parameter is not present, then audio data MUST NOT
   be bundled into the DV video stream.









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RFC 3189      RTP Payload Format for DV (IEC 61834) Video   January 2002


3.1 SDP description for unbundled streams

   When using unbundled mode, the RTP streams for video and audio will
   be sent separately to different ports or different multicast groups.
   When this is done, SDP carries several m=?? lines, one for each media
   type of the session (see RFC 2327 [13]).

   An example SDP description using these attributes is:

      v=0
      o=ikob 2890844526 2890842807 IN IP4 126.16.64.4
      s=POI Seminar
      i=A Seminar on how to make Presentations on the Internet
      u=http://www.koganei.wide.ad.jp/~ikob/POI/index.html
      e=ikob@koganei.wide.ad.jp (Katsushi Kobayashi)
      c=IN IP4 224.2.17.12/127
      t=2873397496 2873404696
      m=audio 49170 RTP/AVP 112
      a=rtpmap:112 L16/32000/2
      m=video 50000 RTP/AVP 113
      a=rtpmap:113 DV/90000
      a=fmtp:113 encode=SD-VCR/525-60
      a=fmtp:113 audio=none

   This describes a session where audio and video streams are sent
   separately.  The session is sent to a multicast group 224.2.17.12.
   The audio is sent using L16 format, and the video is sent using SD-
   VCR 525/60 format which corresponds to NTSC format in consumer DV.

3.2 SDP description for bundled streams

   When sending a bundled stream, all the DIF blocks including system
   data will be sent through a single RTP stream.  An example SDP
   description for a bundled DV stream is:

















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RFC 3189      RTP Payload Format for DV (IEC 61834) Video   January 2002


      v=0
      o=ikob 2890844526 2890842807 IN IP4 126.16.64.4
      s=POI Seminar
      i=A Seminar on how to make Presentations on the Internet
      u=http://www.koganei.wide.ad.jp/~ikob/POI/index.html
      e=ikob@koganei.wide.ad.jp (Katsushi Kobayashi)
      c=IN IP4 224.2.17.12/127
      t=2873397496 2873404696
      m=video 49170 RTP/AVP 112 113
      a=rtpmap:112 DV/90000
      a=fmtp: 112 encode=SD-VCR/525-60
      a=fmtp: 112 audio=bundled
      a=fmtp: 113 encode=306M/525-60
      a=fmtp: 113 audio=bundled

   This SDP record describes a session where audio and video streams are
   sent bundled.  The session is sent to a multicast group 224.2.17.12.
   The video is sent using both 525/60 consumer DV and SMPTE standard
   306M formats, when the payload type is 112 and 113, respectively.

4. Security Considerations

   RTP packets using the payload format defined in this specification
   are subject to the security considerations discussed in the RTP
   specification [6], and any appropriate RTP profile.  This implies
   that confidentiality of the media streams is achieved by encryption.
   Because the data compression used with this payload format is applied
   to end-to-end, encryption may be performed after compression so there
   is no conflict between the two operations.

   A potential denial-of-service threat exists for data encodings using
   compression techniques that have non-uniform receiver-end
   computational load.  The attacker can inject pathological datagrams
   into the stream which are complex to decode and cause the receiver to
   be overloaded.  However, this encoding does not exhibit any
   significant non-uniformity.

   As with any IP-based protocol, in some circumstances a receiver may
   be overloaded simply by the receipt of too many packets, either
   desired or undesired.  Network-layer authentication may be used to
   discard packets from undesired sources, but the processing cost of
   the authentication itself may be too high.  In a multicast
   environment, pruning of specific sources may be implemented in future
   versions of IGMP [14] and in multicast routing protocols to allow a
   receiver to select which sources are allowed to reach it.






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RFC 3189      RTP Payload Format for DV (IEC 61834) Video   January 2002


5. IANA Considerations

   This document defines a new RTP payload name and associated MIME
   type, DV.  The registration forms for the MIME types for both video
   and audio are shown in the next sections.

5.1 DV video MIME registration form

   MIME media type name: video

   MIME subtype name: DV

   Required parameters:
      encode: type of DV format.  Permissible values for encode are
         SD-VCR/525-60, SD-VCR/625-50, HD-VCR/1125-60 HD-VCR/1250-50,
         SDL-VCR/525-60, SDL-VCR/625-50, 306M/525-60, 306M/625-50,
         314M-25/525-60, 314M-25/625-50, 314M-50/525-60, and
         314M-50/625-50.

   Optional parameters:
      audio: whether the DV stream includes audio data or not.
         Permissible values for audio are bundled and none.  Defaults to
         none.

   Encoding considerations:
      DV video can be transmitted with RTP as specified in RFC 3189.
      Other transport methods are not specified.

   Security considerations:
      See Section 4 of RFC 3189.

   Interoperability considerations: NONE

   Published specification: IEC 61834 Standard
      SMPTE 306M
      SMPTE 314M
      RFC 3189

   Applications which use this media type:
      Video communication.

   Additional information: None
      Magic number(s): None
      File extension(s): None
      Macintosh File Type Code(s): None






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RFC 3189      RTP Payload Format for DV (IEC 61834) Video   January 2002


   Person & email address to contact for further information:
      Katsushi Kobayashi
      e-mail: ikob@koganei.wide.ad.jp

   Intended usage: COMMON

   Author/Change controller:
      Katsushi Kobayashi
      e-mail: ikob@koganei.wide.ad.jp

5.2 DV audio MIME registration form

   MIME media type name: audio

   MIME subtype name: DV

   Required parameters:
      encode: type of DV format.  Permissible values for encode are
         SD-VCR/525-60, SD-VCR/625-50, HD-VCR/1125-60 HD-VCR/1250-50,
         SDL-VCR/525-60, SDL-VCR/625-50, 306M/525-60, 306M/625-50,
         314M-25/525-60, 314M-25/625-50, 314M-50/525-60, and
         314M-50/625-50.

   Optional parameters: NONE

   Encoding considerations:
      DV audio can be transmitted with RTP as specified in RFC 3189.
      Other transport methods are not specified.

   Security considerations:
      See Section 4 of RFC 3189.

   Interoperability considerations: NONE

   Published specification: IEC 61834 Standard
      SMPTE 306M
      SMPTE 314M
      RFC 3189

   Applications which use this media type:
      Audio communication.

   Additional information: None
      Magic number(s): None
      File extension(s): None
      Macintosh File Type Code(s): None





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RFC 3189      RTP Payload Format for DV (IEC 61834) Video   January 2002


   Person & email address to contact for further information:
      Katsushi Kobayashi
      e-mail: ikob@koganei.wide.ad.jp

   Intended usage: COMMON

   Author/Change controller:
      Katsushi Kobayashi
      e-mail: ikob@koganei.wide.ad.jp

6. References

   [1]   IEC 61834, Helical-scan digital video cassette recording system
         using 6,35 mm magnetic tape for consumer use (525-60, 625-50,
         1125-60 and 1250-50 systems).

   [2]   IEC 61883, Consumer audio/video equipment - Digital interface.

   [3]   IEEE Std 1394-1995, Standard for a High Performance Serial Bus

   [4]   SMPTE 306M, 6.35-mm type D-7 component format - video
         compression at 25Mb/s -525/60 and 625/50.

   [5]   SMPTE 314M, Data structure for DV-based audio and compressed
         video 25 and 50Mb/s.

   [6]   Schulzrinne, H., Casner, S., Frederick, R. and V. Jacobson,
         "RTP: A transport protocol for real-time applications", RFC
         1889, January 1996.

   [7]   Hoffman, D., Fernando, G., Goyal, V. and M. Civanlar, "RTP
         Payload Format for MPEG1/MPEG2 Video", RFC 2250, January 1998.

   [8]   Bradner, S., "Key words for use in RFCs to Indicate Requirement
         Levels", BCP 14, RFC 2119, March 1997.

   [9]   ISO/IEC 11172, Coding of moving pictures and associated audio
         for digital storage media up to about 1,5 Mbits/s.

   [10]  ISO/IEC 13818, Generic coding of moving pictures and associated
         audio information.

   [11]  Schulzrinne, H., "RTP Profile for Audio and Video Conferences
         with Minimal Control", RFC 1890, January 1996.

   [12]  Kobayashi, K., Ogawa, A., Casner S. and C. Bormann, "RTP
         Payload Format for 12-bit DAT Audio and 20- and 24-bit Linear
         Sampled Audio", RFC 3190, January 2002.



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RFC 3189      RTP Payload Format for DV (IEC 61834) Video   January 2002


   [13]  Handley, M. and V. Jacobson, "SDP: Session Description
         Protocol", RFC 2327, April 1998.

   [14]  Deering, S., "Host Extensions for IP Multicasting", STD 5, RFC
         1112, August 1989.

7. Authors' Addresses

   Katsushi Kobayashi
   Communication Research Laboratory
   4-2-1 Nukii-kitamachi,
   Koganei Tokyo 184-8795 JAPAN

   EMail: ikob@koganei.wide.ad.jp


   Akimichi Ogawa
   Keio University
   5322 Endo,
   Fujisawa Kanagawa 252 JAPAN

   EMail: akimichi@sfc.wide.ad.jp


   Stephen L. Casner
   Packet Design
   2465 Latham Street
   Mountain View, CA 94040 United States

   EMail: casner@acm.org


   Carsten Bormann
   Universitaet Bremen TZI
   Postfach 330440
   D-28334 Bremen, Germany

   Phone: +49 421 218 7024
   Fax:   +49 421 218 7000
   EMail: cabo@tzi.orgEMail: cabo@tzi.org











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RFC 3189      RTP Payload Format for DV (IEC 61834) Video   January 2002


8.  Full Copyright Statement

   Copyright (C) The Internet Society (2002).  All Rights Reserved.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph are
   included on all such copies and derivative works.  However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the purpose of
   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than
   English.

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assigns.

   This document and the information contained herein is provided on an
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS 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.

Acknowledgement

   Funding for the RFC Editor function is currently provided by the
   Internet Society.



















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