path: root/doc/rfc/rfc6469.txt

Internet Engineering Task Force (IETF)                      K. Kobayashi
Request for Comments: 6469                                   AICS, RIKEN
Obsoletes: 3189                                               K. Mishima
Category: Standards Track                                Keio University
ISSN: 2070-1721                                                S. Casner
                                                           Packet Design
                                                              C. Bormann
                                                 Universitaet Bremen TZI
                                                           December 2011


              RTP Payload Format for DV (IEC 61834) Video

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).  This
   document obsoletes RFC 3189.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6469.

Copyright Notice

   Copyright (c) 2011 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.



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   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
   10, 2008.  The person(s) controlling the copyright in some of this
   material may not have granted the IETF Trust the right to allow
   modifications of such material outside the IETF Standards Process.
   Without obtaining an adequate license from the person(s) controlling
   the copyright in such materials, this document may not be modified
   outside the IETF Standards Process, and derivative works of it may
   not be created outside the IETF Standards Process, except to format
   it for publication as an RFC or to translate it into languages other
   than English.

Table of Contents

   1. Introduction ....................................................3
      1.1. Terminology ................................................4
   2. RTP Payload Format ..............................................4
      2.1. The DV Format Encoding .....................................4
      2.2. RTP Header Usage ...........................................5
      2.3. Payload Structures .........................................6
   3. Payload Format Parameters .......................................7
      3.1. Media Type Registration ....................................7
           3.1.1. Media Type Registration for DV Video ................8
           3.1.2. Media Type Registration for DV Audio ................9
      3.2. SDP Parameters ............................................11
           3.2.1. Mapping of Payload Type Parameters to SDP ..........11
           3.2.2. Usage with the SDP Offer/Answer Model ..............12
      3.3. Examples ..................................................12
           3.3.1. Example for Unbundled Streams ......................13
           3.3.2. Example for Bundled Streams ........................13
   4. Security Considerations ........................................14
   5. Congestion Control .............................................14
   6. IANA Considerations ............................................14
   7. Major Changes from RFC 3189 ....................................15
   8. Interoperability with Previous Implementations .................15
   9. Acknowledgment .................................................16
   10. References ....................................................16
      10.1. Normative References .....................................16
      10.2. Informative References ...................................17












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1.  Introduction

   This document specifies payload formats for encapsulating both
   consumer- and professional-use Digital Video (DV) format data streams
   into the Real-Time Transport Protocol (RTP) [RFC3550].  DV
   compression audio and video formats were designed for a recording
   format on 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, Discrete Cosine Transform (DCT)
   video encoding format, and audio encoding format [IEC61834].  The
   digital interface part of IEC 61883 defines an interface on the IEEE
   1394 system [IEC61883][IEEE1394].  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 the Society of Motion Picture and
   Television Engineers (SMPTE) as 314M and 370M, for different sampling
   systems, higher color resolution, and higher bit rates
   [SMPTE314M][SMPTE370M].

   In summary, 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 314M
   and 370M.  Both encoding formats are based on consumer DV and used in
   SMPTE D-7, D-9, and D-12 video systems.  The RTP payload format
   specified in this document supports IEC 61834 consumer DV and
   professional SMPTE 314M and 370M (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 [RFC2250] and elsewhere.

   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).  It also supports
   eight of the SMPTE standards: 314M 25 Mbit/s (525/60, 625/50), 314M
   50 Mbit/s (525/60, 625/50), and 370M 100 Mbit/s (1080/60i, 1080/50i,
   720/60p, and 720/50p).  In the future, it can be extended into other
   video formats managed by the 80-byte DV Digital Interface Format
   (DIF) block.





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   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 [RFC2119].

2.  RTP Payload Format

2.1.  The 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 [ISO/IEC11172][ISO/IEC13818].  All video data, including
   audio and other system data, is managed within the picture frame unit
   of video.

   The DV video encoding is composed of a three-level hierarchical
   structure, i.e., DCT super block, DCT macro block, and DCT block.  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, and each DCT macro block consists of
   a number of DCT blocks.  Each DCT block consists of 8x8 pixels and
   represents a rectangle region for each color, Y, Cb, and Cr.

   Audio data is encoded in Pulse Code Modulation (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 [IEC61834][SMPTE314M]
   [SMPTE370M].

   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 (VAUX) information, Audio, and Video.  Audio
   DIF blocks are composed of 5 bytes of Audio Auxiliary (AAUX) data and
   72 bytes of audio data.






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   Each RTP packet starts with the RTP header as defined in RFC 3550
   [RFC3550].  No additional payload-format-specific header is required
   for this payload format.

2.2.  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 DV frame
   time, as given in the following table:

   +----------+----------------+---------------------------------------+
   |   Mode   |   Frame rate   |  Increase of 90 kHz timestamp per DV  |
   |          |      (Hz)      |                 frame                 |
   +----------+----------------+---------------------------------------+
   |  525-60  |      29.97     |                  3003                 |
   |  625-50  |       25       |                  3600                 |
   |  1125-60 |       30       |                  3000                 |
   |  1250-50 |       25       |                  3600                 |
   | 1080-60i |      29.97     |                  3003                 |
   | 1080-50i |       25       |                  3600                 |
   |  720-60p |      59.94     |                3003(*)                |
   |  720-50p |       50       |                3600(*)                |
   +----------+----------------+---------------------------------------+

   (*) Note that even in the 720-line DV system, the data in two video
   frames shall be processed within one DV frame duration of the 1080-
   line system.  Audio data and subcode data in the 720-line system are
   processed in the same way as the 1080-line system.  Therefore, in the
   720-line system, the timestamp increase given in the third column
   corresponds to two video frames time.

   Marker bit (M): The marker bit of the RTP fixed header is set to one
   on the last packet of a video frame; on other packets, it 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



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   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.

2.3.  Payload Structures

   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, but 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 could
   omit the DIF sequence header and subcode DIF blocks from a stream
   when the information either is known from out-of-band sources or is
   not required for the application.  Note that time code in DIF blocks
   is mandatory for professional video applications.  When unbundled
   audio and video streams are sent, any DIF sequence header and subcode
   DIF blocks MUST be included and sent in the video stream.

   DV streams include "source" and "source control" packs that carry
   information indispensable for proper decoding, such as video signal
   type, frame rate, aspect ratio, picture position, quantization of
   audio sampling, number of audio samples in a frame, 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) [RFC4566] parameters
   for these attributes are defined in this document.  Instead, the RTP
   sender MUST transmit at least those VAUX (Video Auxiliary) DIF blocks
   and/or audio DIF blocks with AAUX (Audio Auxiliary) information bytes
   that include "source" and "source control" packs containing 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.



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   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) [RFC3551][RFC3190] in order to maximize interoperability with
   non-DV-capable receivers while maintaining the original source
   quality.

   In the case of unbundled transmission that is compelled to use both
   audio and video 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 RTP Control
   Protocol (RTCP) as described in [RFC3550].  In this case, the audio
   stream uses the 90 kHz clock rate, and the timestamp uses the same
   clock rate as the video.

   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 that 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.  Payload Format Parameters

   This section specifies the parameters that MAY be used to select
   optional features of the payload format and certain features of the
   bitstream.  The parameters are specified here as part of the media
   type registration for the DV encoding.  A mapping of the parameters
   into the Session Description Protocol (SDP) [RFC4566] is also
   provided for applications that use SDP.  Equivalent parameters could
   be defined elsewhere for use with control protocols that do not use
   SDP.

3.1.  Media Type Registration

   This registration is done using the template defined in RFC 4288
   [RFC4288] and following RFC 4855 [RFC4855].




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3.1.1.  Media Type Registration for DV Video

   Type name:  video

   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
         314M-25/525-60
         314M-25/625-50
         314M-50/525-60
         314M-50/625-50
         370M/1080-60i
         370M/1080-50i
         370M/720-60p
         370M/720-50p
         306M/525-60 (for backward compatibility)
         306M/625-50 (for backward compatibility)

   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 6469
         (this document).  Other transport methods are not specified.

   Security considerations:

         See Section 4 of RFC 6469 (this document).

   Interoperability considerations:  Interoperability with previous
      implementations is discussed in Section 8.








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   Public specifications:

         IEC 61834 Standard
         SMPTE 314M
         SMPTE 370M
         RFC 6469 (this document)
         SMPTE 306M (for backward compatibility)

   Applications that use this media type:  Audio and video streaming and
      conferencing tools.

   Additional information:  NONE

   Person & email address to contact for further information:

         Katsushi Kobayashi
         ikob@riken.jp

   Intended usage:  COMMON

   Restrictions on usage:  This media type depends on RTP framing and
      hence is only defined for transfer via RTP [RFC3550].  Transfer
      within other framing protocols is not defined at this time.

   Author:

         Katsushi Kobayashi

   Change controller:

         IETF Audio/Video Transport working group delegated from the
         IESG

3.1.2.  Media Type Registration for DV Audio

   Type name:  audio

   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



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         314M-25/525-60
         314M-25/625-50
         314M-50/525-60
         314M-50/625-50
         370M/1080-60i
         370M/1080-50i
         370M/720-60p
         370M/720-50p
         306M/525-60 (for backward compatibility)
         306M/625-50 (for backward compatibility)

   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 audio can be transmitted with RTP as specified in RFC 6469
         (this document).  Other transport methods are not specified.

   Security considerations:

         See Section 4 of RFC 6469 (this document).

   Interoperability considerations:  Interoperability with previous
      implementations is discussed in Section 8.

   Published specifications:

         IEC 61834 Standard
         SMPTE 314M
         SMPTE 370M
         RFC 6469 (this document)
         SMPTE 306M (for backward compatibility).

   Applications that use this media type:  Audio and video streaming and
      conferencing tools.

   Additional information:  NONE

   Person & email address to contact for further information:

         Katsushi Kobayashi
         ikob@riken.jp

   Intended usage:  COMMON



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   Restrictions on usage:  This media type depends on RTP framing and
      hence is only defined for transfer via RTP [RFC3550].  Transfer
      within other framing protocols is not defined at this time.

   Author:

         Katsushi Kobayashi

   Change controller:

         IETF Audio/Video Transport working group delegated from the
         IESG

3.2.  SDP Parameters

3.2.1.  Mapping of Payload Type Parameters to SDP

   The information carried in the media type specification has a
   specific mapping to fields in the Session Description Protocol (SDP),
   which is commonly used to describe RTP sessions.  When SDP is used to
   specify sessions employing the DV encoding, the mapping is as
   follows:

   o  The media type ("video") goes in SDP "m=" as the media name.

   o  The media subtype ("DV") goes in SDP "a=rtpmap" as the encoding
      name.  The RTP clock rate in "a=rtpmap" MUST be 90000, which for
      the payload format defined in this document is a 90 kHz clock.

   o  Any remaining parameters go in the SDP "a=fmtp" attribute by
      copying them directly from the media type string as a semicolon-
      separated list of parameter=value pairs.

   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 "encode" specifies which type of DV format is
   used.  The DV format name will be one of the following values:

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



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      314M-25/625-50
      314M-50/525-60
      314M-50/625-50
      370M/1080-60i
      370M/1080-50i
      370M/720-60p
      370M/720-50p
      306M/525-60 (for backward compatibility)
      306M/625-50 (for backward compatibility)

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

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

   The optional parameter "audio" will be one of the following values:

      bundled
      none (default)

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

3.2.2.  Usage with the SDP Offer/Answer Model

   The following considerations apply when using SDP offer/answer
   procedures [RFC3264] to negotiate the use of the DV payload in RTP:

   o  The "encode" parameter can be used for sendrecv, sendonly, and
      recvonly streams.  Each encode type MUST use a separate payload
      type number.

   o  Any unknown parameter in an offer MUST be ignored by the receiver
      and MUST NOT be included in the answer.

   In an offer for unbundled streams, the group attribute as defined in
   the Session Description Protocol (SDP) Grouping Framework [RFC5888]
   can be used in order to associate the related audio and video.  The
   example usage of SDP grouping is detailed in [RFC5888].

3.3.  Examples

   Some example SDP session descriptions utilizing DV encoding formats
   follow.






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3.3.1.  Example 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 unbundled audio and video streams are sent, SDP carries several
   "m=" lines, one for each media type of the session (see [RFC4566]).

   An example SDP description using these attributes is:

     v=0
     o=ikob 2890844526 2890842807 IN IP4 192.0.2.1
     s=POI Seminar
     i=A Seminar on how to make Presentations on the Internet
     u=http://www.example.net/~ikob/POI/index.html
     e=ikob@example.net (Katsushi Kobayashi)
     c=IN IP4 233.252.0.1/127
     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 audio=none

   This describes a session where audio and video streams are sent
   separately.  The session is sent to a multicast group 233.252.0.1.
   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.

3.3.2.  Example 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:

     v=0
     o=ikob 2890844526 2890842807 IN IP4 192.0.2.1
     s=POI Seminar
     i=A Seminar on how to make Presentations on the Internet
     u=http://www.example.net/~ikob/POI/index.html
     e=ikob@example.net (Katsushi Kobayashi)
     c=IN IP4 233.252.0.1/127
     t=2873397496 2873404696
     m=video 49170 RTP/AVP 112 113
     a=rtpmap:112 DV/90000
     a=fmtp:112 encode=SD-VCR/525-60 audio=bundled
     a=fmtp:113 encode=314M-50/525-60 audio=bundled



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   This SDP record describes a session where audio and video streams are
   sent bundled.  The session is sent to a multicast group 233.252.0.1.
   The video is sent using both 525/60 consumer DV and SMPTE standard
   314M 50 Mbit/s 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 [RFC3550] 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 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 that 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, mechanisms for joining and pruning of specific sources
   are specified in IGMPv3, Multicast Listener Discovery Version 2
   (MLDv2) [RFC3376][RFC3810] or Lightweight-IGMPv3 (LW-IGMPv3),
   LW-MLDv2 [RFC5790] and in multicast routing protocols to allow a
   receiver to select which sources are allowed to reach it [RFC4607].

5.  Congestion Control

   The general congestion control considerations for transporting RTP
   data apply; see RTP [RFC3550] and any applicable RTP profile like
   Audio-Visual Profile (AVP) [RFC3551].

6.  IANA Considerations

   This document obsoletes [RFC3189], and some registration forms have
   been updated by this document.  The registration forms (based on the
   RFC 4855 [RFC4855] definition) for the media types for both video and
   audio are shown in Section 3.1.





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7.  Major Changes from RFC 3189

   The changes from [RFC3189] are:

   1.  Specified that support for SMPTE 306M is only for backward
       interoperability, since it is covered by SMPTE 314M format.

   2.  Added SMPTE 370M 100 Mbit/s High Definition Television (HDTV)
       (1080/60i, 1080/50i, 720/60p, and 720/50p) format.

   3.  Incorporated the Source-Specific Multicast (SSM) specification
       for avoiding overloaded traffic source in multicast usage.  Added
       a reference to the Source-Specific Multicast (SSM) specification
       as a way to reduce unwanted traffic in a multicast application.

   4.  Clarified the case where a sender omits subcode DIF block data
       from the stream.

   5.  Added considerations for the offer/answer model.

   6.  Revised media types registration form based on new registration
       rule [RFC4855].

8.  Interoperability with Previous Implementations

   In this section, we discuss interoperability with implementations
   based on [RFC3189], which is obsoleted by this document.

   [RFC3189] regards SMPTE 306M [SMPTE306M] and SMPTE 314M [SMPTE314M]
   as different encoding formats, although the format of SMPTE 306M is
   already covered by SMPTE 314M.  Therefore, this document recommends
   that the definition depending on SMPTE 306M SHOULD NOT be used, and
   SMPTE 314M SHOULD be used instead.  An RTP application could handle a
   stream identified in SMPTE 306M encoding as SMPTE 314M encoding
   instead.

   An offer MAY include SMPTE 306M encoding coming from a legacy system,
   and receivers SHOULD support this value.

   If an initial offer that did not include SMPTE 306M was rejected, the
   offerer MAY try a new offer with SMPTE 306M.  For this case, an RTP
   application MAY handle a stream identified in SMPTE 306M encoding as
   SMPTE 314M encoding instead.

   In addition, the SDP examples in [RFC3189] provide incorrect SDP
   "a=fmtp" attribute usage.





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9.  Acknowledgment

   Thanks to Akimichi Ogawa, a former author of this document.

10.  References

10.1.  Normative References

   [IEC61834]      IEC, "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)".

   [RFC2119]       Bradner, S., "Key words for use in RFCs to Indicate
                   Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC3190]       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.

   [RFC3264]       Rosenberg, J. and H. Schulzrinne, "An Offer/Answer
                   Model with Session Description Protocol (SDP)",
                   RFC 3264, June 2002.

   [RFC3550]       Schulzrinne, H., Casner, S., Frederick, R., and V.
                   Jacobson, "RTP: A Transport Protocol for Real-Time
                   Applications", STD 64, RFC 3550, July 2003.

   [RFC3551]       Schulzrinne, H. and S. Casner, "RTP Profile for Audio
                   and Video Conferences with Minimal Control", STD 65,
                   RFC 3551, July 2003.

   [RFC4288]       Freed, N. and J. Klensin, "Media Type Specifications
                   and Registration Procedures", BCP 13, RFC 4288,
                   December 2005.

   [RFC4566]       Handley, M., Jacobson, V., and C. Perkins, "SDP:
                   Session Description Protocol", RFC 4566, July 2006.

   [RFC4855]       Casner, S., "Media Type Registration of RTP Payload
                   Formats", RFC 4855, February 2007.

   [RFC5888]       Camarillo, G. and H. Schulzrinne, "The Session
                   Description Protocol (SDP) Grouping Framework",
                   RFC 5888, June 2010.

   [SMPTE306M]     SMPTE, "SMPTE 306M, 6.35-mm Type D-7 Component Format
                   - Video Compression at 25Mb/s - 525/60 and 625/50".



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   [SMPTE314M]     SMPTE, "SMPTE 314M, Data Structure for DV-Based Audio
                   and Compressed Video - 25 and 50Mb/s".

   [SMPTE370M]     SMPTE, "SMPTE 370M, Data Structure for DV-Based
                   Audio, Data and Compressed Video at 100 Mb/s 1080/
                   60i, 1080/50i, 720/60p, and 720/50p".

10.2.  Informative References

   [IEC61883]      IEC, "IEC 61883, Consumer audio/video equipment -
                   Digital interface".

   [IEEE1394]      IEEE, "IEEE Std 1394-1995, Standard for a High
                   Performance Serial Bus".

   [ISO/IEC11172]  ISO/IEC, "ISO/IEC 11172, Coding of moving pictures
                   and associated audio for digital storage media up to
                   about 1,5 Mbit/s".

   [ISO/IEC13818]  ISO/IEC, "ISO/IEC 13818, Generic coding of moving
                   pictures and associated audio information".

   [RFC2250]       Hoffman, D., Fernando, G., Goyal, V., and M.
                   Civanlar, "RTP Payload Format for MPEG1/MPEG2 Video",
                   RFC 2250, January 1998.

   [RFC3189]       Kobayashi, K., Ogawa, A., Casner, S., and C. Bormann,
                   "RTP Payload Format for DV (IEC 61834) Video",
                   RFC 3189, January 2002.

   [RFC3376]       Cain, B., Deering, S., Kouvelas, I., Fenner, B., and
                   A. Thyagarajan, "Internet Group Management Protocol,
                   Version 3", RFC 3376, October 2002.

   [RFC3810]       Vida, R. and L. Costa, "Multicast Listener Discovery
                   Version 2 (MLDv2) for IPv6", RFC 3810, June 2004.

   [RFC4607]       Holbrook, H. and B. Cain, "Source-Specific Multicast
                   for IP", RFC 4607, August 2006.

   [RFC5790]       Liu, H., Cao, W., and H. Asaeda, "Lightweight
                   Internet Group Management Protocol Version 3 (IGMPv3)
                   and Multicast Listener Discovery Version 2 (MLDv2)
                   Protocols", RFC 5790, February 2010.







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Authors' Addresses

   Katsushi Kobayashi
   Advanced Institute for Computational Science, RIKEN
   7-1-26 Minatojima-minami
   Chuo-ku, Kobe, Hyogo  760-0045
   Japan

   EMail: ikob@riken.jp


   Kazuhiro Mishima
   Keio University
   5322 Endo
   Fujisawa, Kanagawa  252-8520
   Japan

   EMail: three@sfc.wide.ad.jp


   Stephen L. Casner
   Packet Design
   2455 Augustine Drive
   Santa Clara, CA  95054
   United States

   EMail: casner@acm.org


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

   Phone: +49 421 218 63921
   Fax:   +49 421 218 7000
   EMail: cabo@tzi.org













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