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Network Working Group                                       K. KobayashiRequest for Comments: 3189             Communication Research LaboratoryCategory: Standards Track                                       A. Ogawa                                                         Keio University                                                               S. Casner                                                           Packet Design                                                              C. Bormann                                                 Universitaet Bremen TZI                                                            January 2002RTP Payload Format for DV (IEC 61834) VideoStatus 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 standardsKobayashi, et al.           Standards Track                     [Page 1]

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 inRFC 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 inRFC 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.Kobayashi, et al.           Standards Track                     [Page 2]

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 inRFC 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                      3600Kobayashi, et al.           Standards Track                     [Page 3]

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.Kobayashi, et al.           Standards Track                     [Page 4]

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 inRFC 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/90000Kobayashi, et al.           Standards Track                     [Page 5]

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.Kobayashi, et al.           Standards Track                     [Page 6]

RFC 3189      RTP Payload Format for DV (IEC 61834) Video   January 20023.1 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 (seeRFC 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:Kobayashi, et al.           Standards Track                     [Page 7]

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.Kobayashi, et al.           Standards Track                     [Page 8]

RFC 3189      RTP Payload Format for DV (IEC 61834) Video   January 20025. 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 inRFC 3189.      Other transport methods are not specified.   Security considerations:      SeeSection 4 of RFC 3189.   Interoperability considerations: NONE   Published specification: IEC 61834 Standard      SMPTE 306M      SMPTE 314MRFC 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): NoneKobayashi, et al.           Standards Track                     [Page 9]

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.jp5.2 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 inRFC 3189.      Other transport methods are not specified.   Security considerations:      SeeSection 4 of RFC 3189.   Interoperability considerations: NONE   Published specification: IEC 61834 Standard      SMPTE 306M      SMPTE 314MRFC 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): NoneKobayashi, et al.           Standards Track                    [Page 10]

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.jp6. 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",RFC1889, 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.Kobayashi, et al.           Standards Track                    [Page 11]

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,RFC1112, 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.orgKobayashi, et al.           Standards Track                    [Page 12]

RFC 3189      RTP Payload Format for DV (IEC 61834) Video   January 20028.  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.Kobayashi, et al.           Standards Track                    [Page 13]