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Versions: 00 01 02 03 04 rfc3189                                        
 INTERNET-DRAFT                                       Katsushi Kobayashi
 draft-ietf-avt-dv-video-03.txt        Communication Research Laboratory
                                                          Akimichi Ogawa
                                                         Keio University
                                                          Stephen Casner
                                                           Cisco Systems
                                                         Carsten Bormann
                                                 Universitaet Bremen TZI
                                                           June 26, 2000
                                                   Expires December 2000

                 RTP Payload Format for DV Format Video

Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC 2026.

      Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet- Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

1. 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).  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(D-7)
   and 314M(D-9).  Both are based on consumer DV.  The RTP payload
   format specified in this document supports IEC 61834 consumer DV and
   professional SMPTE 306M and 314M(DV-Based) formats.



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

   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.

   2.1 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]

3. 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



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   data are managed within the picture frame unit of video.

   The DV 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. 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.

4.1 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



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     1125-60        30                      3000
     1250-50        25                      3600

   When the DV stream is obtained from a IEEE 1394 interface, the
   progress of video frame times MAY be monitored using the SYT
   timestamp carried in the CIP header, as described in Appendix A.

   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 done by differences in RTP timestamp.

4.2 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 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
   send DIF-sequence header and subcode DIF block into streams.  When
   sending DIF-sequence header and subcode DIF block, both the 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,
   position of picture, quantization of audio sampling, the number of
   audio channels, audio channel assignment, and language of audio.
   However, describing all of these attributes with SDP would require
   large SDP descriptions to enumerate all combinations.  Therefore, in
   the later section of this document, the SDP entry for each of these
   parameters is not defined.  Instead, the RTP sender MUST transmit at
   least VAUX DIF block and/or AAUX information including "source" and



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   "source control" pack filled with the indispensable information for
   decoding.  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.

5. SDP Signaling for RTP/DV

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

   When DV stream is sent to port 31394 and 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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   "DV" is the encoding name for the DV video payload format defined in
   this document. 90000 shows the clock rate. The clock used for the
   payload format defined in this document uses 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 parameter <DV-video encoding> is specified which type of DV
   format is used. The DV format name will be one of the following:

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

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

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

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

         o  bundled
         o  none     (default)

   When the fmtp audio: parameter is not announced, the audio data MUST
   not be bundled into the DV video stream.

5.1 SDP description for unbundled stream

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



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   An example of SDP description using these attributes is:

      v=0
      o=ikob 2890844526 2890842807 IN IP4 126.16.64.4
      s=POI Seminar
      i=A Seminar of how to make Presentation 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.

5.2 SDP description for bundled stream

   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:

      v=0
      o=ikob 2890844526 2890842807 IN IP4 126.16.64.4
      s=POI Seminar
      i=A Seminar of how to make Presentation 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

   Above 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.



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6. 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.

7. MIME registration

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

   7.1 DV video 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 DV stream includes audio data or not.
          Permissible values for audio are bundled and none. Defaults



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          to none.

     Encoding considerations: DV video can be transmitted with
        RTP as specified in "draft-ietf-avt-dv-video-02".

     Security considerations: None

     Interoperability considerations: NONE

     Published specification: IEC 61834 Standard
                              SMPTE 306M
                              SMPTE 314M
                              draft-ietf-avt-dv-video-02

     Applications which use this media type:
                              Video communication.

     Additional information: None

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

     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

   7.2 DV audio 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




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     Encoding considerations: DV audio can be transmitted with
        RTP as specified in "draft-ietf-avt-dv-video-02".

     Security considerations: None

     Interoperability considerations: NONE

     Published specification: IEC 61834 Standard
                              SMPTE 306M
                              SMPTE 314M
                              draft-ietf-avt-dv-video-02

     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

     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

8. Full Copyright Statement

   Copyright (C) The Internet Society (1999). 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 Soci-
   ety 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 fol-
   lowed, or as required to translate it into languages other than



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   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 MER-
   CHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE."

9. Authors' Addresses


   Katsushi Kobayashi Communication Research Laboratory 4-2-1 Nukii-kita
   machi, 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 Cisco Systems, Inc.  170 West Tasman Drive San
   Jose, CA 95134-1706 United States EMail: casner@cisco.com

   Carsten Bormann Universitaet Bremen FB3 TZI Postfach 330440 D-28334
   Bremen, GERMANY Phone: +49.421.218-7024 Fax: +49.421.218-7000 EMail:
   cabo@tzi.org

10. Bibliography

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




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

   [8] S. Bradner, "Key words for use in RFCs to Indicate Requirement
       Levels", 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] K. Kobayashi, A. Ogawa, S. Casner and C. Bormann, "RTP Payload
        Format for 12-bit DAT, 20- and 24-bit Linear Sampled Audio",
        internet-draft, work in progress.

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

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


























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