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rfc:rfc6469

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.

Kobayashi, et al. Standards Track [Page 1] RFC 6469 RTP Payload Format for DV Video December 2011

 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

Kobayashi, et al. Standards Track [Page 2] RFC 6469 RTP Payload Format for DV Video December 2011

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.

Kobayashi, et al. Standards Track [Page 3] RFC 6469 RTP Payload Format for DV Video December 2011

 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.

Kobayashi, et al. Standards Track [Page 4] RFC 6469 RTP Payload Format for DV Video December 2011

 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

Kobayashi, et al. Standards Track [Page 5] RFC 6469 RTP Payload Format for DV Video December 2011

 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.

Kobayashi, et al. Standards Track [Page 6] RFC 6469 RTP Payload Format for DV Video December 2011

 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].

Kobayashi, et al. Standards Track [Page 7] RFC 6469 RTP Payload Format for DV Video December 2011

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.

Kobayashi, et al. Standards Track [Page 8] RFC 6469 RTP Payload Format for DV Video December 2011

 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

Kobayashi, et al. Standards Track [Page 9] RFC 6469 RTP Payload Format for DV Video December 2011

       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

Kobayashi, et al. Standards Track [Page 10] RFC 6469 RTP Payload Format for DV Video December 2011

 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

Kobayashi, et al. Standards Track [Page 11] RFC 6469 RTP Payload Format for DV Video December 2011

    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.

Kobayashi, et al. Standards Track [Page 12] RFC 6469 RTP Payload Format for DV Video December 2011

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

Kobayashi, et al. Standards Track [Page 13] RFC 6469 RTP Payload Format for DV Video December 2011

 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.

Kobayashi, et al. Standards Track [Page 14] RFC 6469 RTP Payload Format for DV Video December 2011

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.

Kobayashi, et al. Standards Track [Page 15] RFC 6469 RTP Payload Format for DV Video December 2011

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".

Kobayashi, et al. Standards Track [Page 16] RFC 6469 RTP Payload Format for DV Video December 2011

 [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.

Kobayashi, et al. Standards Track [Page 17] RFC 6469 RTP Payload Format for DV Video December 2011

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

Kobayashi, et al. Standards Track [Page 18]

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