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<rfc category="std" docName="draft-ietf-avt-rfc3189bis-04" ipr="pre5378Trust200902" obsoletes="3189">
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  <!-- ***** FRONT MATTER ***** -->

  <front>
    <!-- The abbreviated title is used in the page header - it is only necessary if the 
         full title is longer than 39 characters -->

    <title abbrev="RTP Payload Format for DV Video">
      RTP Payload Format for DV (IEC 61834) Video
    </title>

    <!-- add 'role="editor"' below for the editors if appropriate -->

    <!-- Another author who claims to be an editor -->

    <author fullname="Katsushi Kobayashi" initials="K.K." surname="Kobayashi">
      <organization abbrev="AIST">
        National Institute of Advanced Industrial Science and Technology
      </organization>
      <address>
        <postal>
          <street>1-18-13 Soto-Kanda</street>
          <!-- Reorder these if your country does things differently -->
          <city>Chiyoda-ku</city>
          <region>Tokyo</region>
          <code>184-8795</code>
          <country>Japan</country>
        </postal>
        <email>ikob@ni.aist.go.jp</email>
        <!-- uri and facsimile elements may also be added -->
      </address>
    </author>

    <author fullname="Kazuhiro Mishima" initials="K.M." surname="Mishima">
      <organization abbrev="Keio University">
        Keio University
      </organization>
      <address>
        <postal>
          <street>5322 Endo</street>
          <city>Fujisawa-city</city>
          <region>Kanagawa</region>
          <code>252-8520</code>
          <country>Japan</country>
        </postal>
        <email>three@sfc.wide.ad.jp</email>
      </address>
    </author>

    <author fullname="Stephen L. Casner" initials="S.C." surname="Casner">
      <organization abbrev="Packet Design">
        Packet Design
      </organization>
      <address>
        <postal>
          <street>2465 Latham Street</street>
          <city>Mountain View</city>
          <region>CA</region>
          <code>94040</code>
          <country>United States</country>
        </postal>
        <email>casner@acm.org</email>
      </address>
    </author>

    <author fullname="Carsten Bormann" initials="C.B." surname="Bormann">
      <organization abbrev="Universitaet Bremen TZI">
        Universitaet Bremen TZI
      </organization>
      <address>
        <postal>
          <street>Postfach 330440</street>
          <city>D-28334</city>
          <region>Bremen</region>
          <code></code>
          <country>German</country>
        </postal>
        <phone>+49 421 218 7024</phone>
        <facsimile>+49 421 218 7000</facsimile>
        <email>cabo@tzi.org</email>
      </address>
    </author>

    <date/>

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    <!-- Meta-data Declarations -->

    <area>General</area>

    <workgroup>Network Working Group</workgroup>

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    <keyword>DV/RTP</keyword>

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    <abstract>
      <t>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.</t>
    </abstract>

  </front>

  <!-- ***** MIDDLE MATTER ***** -->

  <middle>

    <section title="Introduction">
      <t>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 <xref target="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, DCT video encoding format, and audio encoding format <xref target="IEC61834"/>.  The
      digital interface part of IEC 61883 defines an interface on IEEE 1394
      system <xref target="IEC61883"/><xref target="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 SMPTE as 314M and 370M, for different sampling systems, higher
      color resolution, and higher bit rates <xref target="SMPTE314M"/><xref target="SMPTE370M"/>.</t>

      <t>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.</t>

      <t>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 <xref target="RFC2250"/> and others.</t>

      <t>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 seven of the
      SMPTE standards: 314M 25Mbps (525/60, 625/50), 314M 50Mbps (525/60,
      625/50), and 370M 100Mbps (1080/60i, 1080/50i, 720/60p, and 720/50p).
      In the future it can be extended into other video formats managed by
      80 byte DV DIF block.</t>

      <t>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.</t>

      <section title="Termiology">
        <t>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 <xref target="RFC2119"/>.</t>
      </section>

      <section title="The DV Format Encoding">

        <t>The DV format only uses the DCT compression technique within each
        frame, contrasted with the interframe compression of the MPEG video
        standards <xref target="ISO/IEC11172"/><xref target="ISO/IEC13818"/>.
        All video data, including audio and other system
        data, are managed within the picture frame unit of video.</t>

        <t>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 represents rectangle region
        for each color, Y, Cb, and Cr, and DCT block consists of 8x8 pixels.</t>

        <t>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.</t>

        <t>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.</t>

        <t>Each RTP packet starts with the RTP header as defined in RFC 3550
        <xref target="RFC3550"/>.  No additional payload-format-specific header is required for
        this payload format.</t>
      </section>
    </section>

    <section title="RTP Payload Format">

      <section title="RTP Header Usage">

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

        <t>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.</t>

        <t>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:</t>

        <texttable>
          <ttcol align='center'>Mode</ttcol>
          <ttcol align='center'>Frame rate (Hz)</ttcol>
          <ttcol align='center'>Increase of one DV frame in 90kHz timestamp</ttcol>

          <c>525-60</c>   <c>29.97</c> <c>3003</c>
          <c>625-50</c>   <c>25</c>    <c>3600</c>
          <c>1125-60</c>  <c>30</c>    <c>3000</c>
          <c>1250-50</c>  <c>25</c>    <c>3600</c>
          <c>1080-60i</c> <c>29.97</c> <c>3003</c>
          <c>1080-50i</c> <c>25</c>    <c>3600</c>
          <c>720-60p</c>  <c>59.94</c> <c>3003(*)</c>
          <c>720-50p</c>  <c>50</c>    <c>3600(*)</c>
        </texttable>

        <t>Note that even in 720-line DV system, the data in two video frame
        shall be processed within one DV frame duration of 1080-line system.
        Audio data and subcode data in 720-line system are processed in the
        same way as the 1080-line system. Therefore  in 720-line system, the
        increase of one DV frame corresponds two video frames time.</t>

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

      <section title="Payload Structures">

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

        <t>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 DIF-sequence header and subcode DIF blocks from a stream, in the
        case of the information either is known out-of-band or is not be
        required for the application.  Note that time code in DIF blocks is
        mandatory for professional video applications. When sending DIF-
        sequence header and subcode DIF blocks with unbundled audio and video
        streams, both types of blocks MUST be included in the video stream.</t>

        <t>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) <xref target="RFC4566"/> parameters for
        these attributes are defined in this document.  Instead, the RTP
        sender MUST transmit at least those VAUX DIF blocks and/or audio DIF
        blocks with AAUX information bytes that include "source" and "source
        control" packs containing the indispensable information for decoding.</t>

        <t>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.</t>

        <t>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.</t>

        <t>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) <xref target="RFC3551"/><xref target="RFC3190"/> in order to maximize interoperability with non-DV- capable
        receivers while maintaining the original source quality.</t>

        <t>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 3550.</t>

        <t>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.</t>
      </section>

    </section>

    <section title="Payload Format Parameters">

      <t>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) <xref target="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.</t>

      <section title="Media Type Registration" anchor="reg_form">

      <t>This registration is done using the template defined in RFC 4288
      <xref target="RFC4288"/> and following RFC 4855 <xref target="RFC4855"/>.</t>

        <section title="Media Type Registration for DV Video">
          <t>
            <list style='hanging'>
              <t hangText="Type name:">video</t>
              <t hangText="Subtype name:">DV</t>
              <t hangText="Required parameters:">
                <list style='hanging'>
                  <t hangText="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), and
                    306M/625-50 (for backward compatibility).</t>
                </list>
              </t>
              <t hangText="Optional parameters:">
                <list style='hanging'>
                  <t hangText="audio:">whether the DV stream includes audio data or not.
                  Permissible values for audio are bundled and none. Defaults to
                  none.</t>
                </list>
              </t>
              <t hangText="Encoding considerations:">
                <list style='empty'>
                  <t>DV video can be transmitted with RTP as specified in RFCXXXX (This
                  document).
                  Other transport methods are not specified.</t>
                </list>
              </t>
              <t hangText="Security considerations:">
                <list style='empty'>
                  <t>See <xref target="sec_cons"/> of RFCXXXX (This document).</t>
                </list>
              </t>
              <t hangText="Interoperability considerations:">NONE</t>
              <t hangText="Public specification:">
                <list style='empty'>
                  <t>IEC 61834 Standard</t>
                  <t>SMPTE 314M</t>
                  <t>SMPTE 370M</t>
                  <t>RFCXXXX (This document)</t>
                  <t>SMPTE 314M (for backward compatibility).</t>
                </list>
              </t>
              <t hangText="Applications that use this media type:">
                  Audio and video streaming and conferencing tools.</t>
              <t hangText="Additional information:">NONE</t>
              <t hangText="Person & email address to contact for further information:">
                <list style='empty'>
                  <t>Katsushi Kobayashi</t>
                  <t>e-mail: ikob@ni.aist.go.jp</t>
                </list>
              </t>
              <t hangText="Intended usage:">COMMON</t>
              <t hangText="Restrictions on usage:">
                  This media type depends on RTP framing, and hence is only
                  defined for transfer via RTP (RFC 3550).  Transfer within
                  other framing protocols is not defined at this time.</t>
              <t hangText="Author:">
                <list style='empty'>
                  <t>Katsushi Kobayashi</t>
                </list>
              </t>
              <t hangText="Change controller:">
                <list style='empty'>
                  <t>IETF Audio/Video Transport working group delegated from the IESG</t>
                </list>
              </t>
            </list>
          </t>
        </section>

        <section title="Media Type Registration for DV Audio">
          <t>
            <list style='hanging'>
              <t hangText="Type name:">audio</t>
              <t hangText="Subtype name:">DV</t>
              <t hangText="Required parameters:">
                <list style='hanging'>
                  <t hangText="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), and
                  306M/625-50 (for backward compatibility).</t>
                </list>
              </t>
              <t hangText="Optional parameters:">
                <list style='hanging'>
                  <t hangText="audio:">whether the DV stream includes audio data or not.
                  Permissible values for audio are bundled and none. Defaults to
                  none.</t>
                </list>
              </t>
              <t hangText="Encoding considerations:">
                <list style='empty'>
                  <t>DV video can be transmitted with RTP as specified in RFCXXXX (This
                  document).
                  Other transport methods are not specified.</t>
                </list>
              </t>
              <t hangText="Security considerations:">
                <list style='empty'>
                  <t>See <xref target="sec_cons"/> of RFCXXXX (This document).</t>
                </list>
              </t>
              <t hangText="Interoperability considerations:">NONE</t>
              <t hangText="Published specification:">
                <list style='empty'>
                  <t>IEC 61834 Standard</t>
                  <t>SMPTE 314M</t>
                  <t>SMPTE 370M</t>
                  <t>RFCXXXX (This document)</t>
                  <t>SMPTE 314M (for backward compatibility).</t>
                </list>
              </t>
              <t hangText="Applications that use this media type:">
                  Audio and video streaming and conferencing tools.</t>
              <t hangText="Additional information:">NONE</t>
              <t hangText="Person & email address to contact for further information:">
                <list style='empty'>
                  <t>Katsushi Kobayashi</t>
                  <t>e-mail: ikob@ni.aist.go.jp</t>
                </list>
              </t>
              <t hangText="Intended usage:">COMMON</t>
              <t hangText="Restrictions on usage:">
                  This media type depends on RTP framing, and hence is only
                  defined for transfer via RTP (RFC 3550).  Transfer within
                  other framing protocols is not defined at this time.</t>
              <t hangText="Author:">
                <list style='empty'>
                  <t>Katsushi Kobayashi</t>
                </list>
              </t>
              <t hangText="Change controller:">
                <list style='empty'>
                  <t>IETF Audio/Video Transport working group delegated from the IESG</t>
                </list>
              </t>
            </list>
          </t>
        </section>
      </section>

      <section title="SDP Parameters">

        <section title="Mapping of Payload Type Parameters to SDP">
        
          <t>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:</t>

          <t>
            <list style='symbols'>
              <t>The media type ("video") goes in SDP "m=" as the media name.</t>
              <t>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 90kHz clock.</t>
              <t>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.</t>
            </list>
          </t>

          <t>Note that the examples in RFC3189 (older version of this document) are
          incorrect on the SDP "a=fmtp" attribute describing.</t>

          <t>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:</t>

          <t>
            <list style='empty'>
            <t>a=fmtp:&lt;payload type&gt; encode=&lt;DV-video encoding&gt;</t>
            </list>
          </t>

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

          <t>
            <list style='empty'>
            <t>SD-VCR/525-60</t>
            <t>SD-VCR/625-50</t>
            <t>HD-VCR/1125-60</t>
            <t>HD-VCR/1250-50</t>
            <t>SDL-VCR/525-60</t>
            <t>SDL-VCR/625-50</t>
            <t>314M-25/525-60</t>
            <t>314M-25/625-50</t>
            <t>314M-50/525-60</t>
            <t>314M-50/625-50</t>
            <t>370M/1080-60i</t>
            <t>370M/1080-50i</t>
            <t>370M/720-60p</t>
            <t>370M/720-50p</t>
            <t>306M/525-60 (for backward compatibility)</t>
            <t>306M/625-50 (for backward compatibility)</t>
            </list>
          </t>

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

          <t>
            <list style='empty'>
            <t>a=fmtp:&lt;payload type&gt; audio=&lt;audio bundled&gt;</t>
            </list>
          </t>

          <t>The optional parameter &lt;audio bundled&gt; will be one of the following:</t>

          <t>
            <list style='empty'>
            <t>bundled</t>
            <t>none (default)</t>
            </list>
          </t>

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

        </section>

        <section title="Usage with the SDP Offer/Answer Model">
          <t>The following considerations apply when using SDP offer-answer
          procedures <xref target="RFC4566"/> to negotiate the use of DV payload in RTP:</t>

          <t>
            <list style='symbols'>
              <t>The "encode" parameter can be used for bi-directional,
                mono-directional and multicast streams. If the offerer sets
                a encode type on a=fmtp field, the answerer MUST select one 
                encode type, and reply with selected encode type value.</t>

              <t>Any unknown parameter in an offer MUST be ignored by the receiver
              and MUST NOT be included in the answer.</t>
            </list>
          </t>

          <t>Some special rules apply for mono-directional traffic:</t>

          <t>
            <list style='symbols'>
              <t>The optional "audio" parameter is only used for the bundled stream.
              On the offerer sets a audio bundled type on a=fmtp field, then the
              answerer MUST select whether the DV stream should be included audio
              data or not, and reply with selected value.</t>
            </list>
          </t>

          <t>Some special rules apply for multicast:</t>

          <t>
            <list style='symbols'>
              <t>The "encode" and "audio" parameter becomes declarative and MUST NOT
              be negotiated.  This parameter is fixed, and a participant MUST use
              the configuration that is provided for the session.</t>
            </list>
          </t>
        </section>
      </section>

      <section title="Examples">

        <t>Some example SDP session descriptions utilizing DV encoding formats
        follow.</t>

        <section title="Example for Unbundled Streams">
          <t>When using unbundled mode, the RTP streams for video and audio will
          be sent separately to different ports or different multicast groups.
          When this is done, SDP carries several m=?? lines, one for each media
          type of the session (see RFC 4566).</t>

          <figure>
            <preamble>An example SDP description using these attributes is:</preamble>
            <artwork><![CDATA[
  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
            ]]></artwork>
            <postamble>
            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.
            </postamble>
          </figure>
        </section>

        <section title="Example for Bundled Streams">
          <t>When sending a bundled stream, all the DIF blocks including system
          data will be sent through a single RTP stream.</t>

          <figure>
            <preamble>An example SDP description for a bundled DV stream is:</preamble>
            <artwork><![CDATA[
  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
            ]]></artwork>
            <postamble>
            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 50Mbps formats, when the payload type is 112 and 113,
            respectively.
            </postamble>
          </figure>
        </section>
      </section>
    </section>

    <section title="Security Considerations" anchor="sec_cons">
      <t>RTP packets using the payload format defined in this specification
      are subject to the security considerations discussed in the RTP
      specification <xref target="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 to end-to-end, encryption may be performed after compression
      so there is no conflict between the two operations.</t>

      <t>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.</t>

      <t>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, joining and pruning mechanism of specific sources is
      specified in IGMPv3 and MLDv2 <xref target="RFC3376"/><xref target="RFC3810"/> and in multicast routing
      protocols to allow a receiver to select which sources are allowed to
      reach it <xref target="RFC4607"/>.</t>
    </section>

    <section title="Congestion Control">
      <t>The general congestion control considerations for transporting RTP
      data apply; see RTP <xref target="RFC3550"/> and any applicable RTP profile like AVP
      <xref target="RFC3551"/>.</t>

      <t>The number of frames encapsulated in each RTP payload highly
      influences the overall bandwidth of the RTP stream due to header
      overhead constraints.  Packetizing more frames in each RTP payload
      can reduce the number of packets sent and hence the header overhead,
      at the expense of increased delay and reduced error robustness.  If
      forward error correction (FEC) is used, the amount of FEC-induced
      redundancy needs to be regulated such that the use of FEC itself does
      not cause a congestion problem.</t>
    </section>

    <section title="IANA Considerations">
      <t>This document defines a new RTP payload name and associated Media
      Type, DV. The registration forms (based on the RFC 4855 <xref target="RFC4855"/> definition)
      for the Media Types for both video and audio are shown in <xref target="reg_form"/>.</t>
    </section>

    <section title="Major Changes from RFC 3189">
      <t>The changes from RFC 3189 are:</t>
      
      <t>
        <list style='format %d.'>
          <t>Removed SMPTE 306M, since it can covered SMPTE 314M format.</t>
          <t>Added SMPTE 370M 100Mbps HDTV (1080/60i, 1080/50i, 720/60p, and
          720/50p) format.</t>
          <t>Incorporated Source Specific Multicast (SSM) spec. for avoiding
          overloaded traffic source in multicast usage.</t>
          <t>Clarified the case that the sender omit subcode DIF block data
          from the stream.</t>
          <t>Added the Offer-Answer Model Consideration.</t>
          <t>Revised Media Types registation form based on new registration
          rule (RFC 4855).</t>
          <t>Revised section structure from based on new example.</t>
        </list>
      </t>
    </section>

    <section title="Interoperability with Previous Implementations">
      <t>In this section, we will specify the interoperability issue with the
      implementations based on RFC obsoleted by this document.</t>

      <t>RFC 3189 regards SMPTE306M <xref target="SMPTE306M"/> and SMPTE314M as different
      encoding format,  although the format of SMPTE 306M is already
      covered SMPTE 314M. Therefore, this document recommends that
      the definition depending on SMPTE306M SHOULD NOT be used, and
      SHOULD use SMPTE314M instead. An RTP application could handle
      a stream identified as SMPTE306M encoding as SMPTE314M one.</t>
    </section>
  </middle>


  <!--  *****BACK MATTER ***** -->

  <back>
    <!-- References split into informative and normative -->

    <!-- There are 2 ways to insert reference entries from the citation libraries:
     1. define an ENTITY at the top, and use "ampersand character"RFC2629; here (as shown)
     2. simply use a PI "less than character"?rfc include="reference.RFC.2119.xml"?> here
        (for I-Ds: include="reference.I-D.narten-iana-considerations-rfc2434bis.xml")

     Both are cited textually in the same manner: by using xref elements.
     If you use the PI option, xml2rfc will, by default, try to find included files in the same
     directory as the including file. You can also define the XML_LIBRARY environment variable
     with a value containing a set of directories to search.  These can be either in the local
     filing system or remote ones accessed by http (http://domain/dir/... ).-->

    <references title="Normative References">
      &RFC3550;
      &RFC3551;
      &RFC2119;
      &RFC3190;
      &RFC4288;
      &RFC4566;
      &RFC4855;

      <reference anchor="IEC61834">
        <!-- the following is the minimum to make xml2rfc happy -->
        <front>
          <title>
         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)
          </title>
          <author>
            <organization>IEC</organization>
          </author>
        </front>
      </reference>

      <reference anchor="SMPTE306M">
        <front>
          <title>
         SMPTE 306M, 6.35-mm type D-7 component format - video
         compression at 25Mb/s -525/60 and 625/50.
          </title>
          <author>
            <organization>SMPTE</organization>
          </author>
        </front>
      </reference>

      <reference anchor="SMPTE314M">
        <front>
          <title>
         SMPTE 314M, Data structure for DV-based audio and compressed
         video 25 and 50Mb/s.
          </title>
          <author>
            <organization>SMPTE</organization>
          </author>
        </front>
      </reference>

      <reference anchor="SMPTE370M">
        <front>
          <title>
         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.
          </title>
          <author>
            <organization>SMPTE</organization>
          </author>
        </front>
      </reference>

    </references>

    <references title="Informative References">
      <!-- Here we use entities that we defined at the beginning. -->
      &RFC2250;
      &RFC3376;
      &RFC3810;
      &RFC4607;

      <reference anchor="ISO/IEC11172">
        <front>
          <title>
         ISO/IEC 11172, Coding of moving pictures and associated audio
         for digital storage media up to about 1,5 Mbits/s.
          </title>
          <author>
            <organization>ISO/IEC</organization>
          </author>
        </front>
      </reference>

      <reference anchor="IEC61883">
        <front>
          <title>
         IEC 61883, Consumer audio/video equipment - Digital interface.
          </title>
          <author>
            <organization>IEC</organization>
          </author>
        </front>
      </reference>

      <reference anchor="IEEE1394">
        <front>
          <title>
         IEEE Std 1394-1995, Standard for a High Performance Serial Bus
          </title>
          <author>
            <organization>IEEE</organization>
          </author>
        </front>
      </reference>

      <reference anchor="ISO/IEC13818">
        <front>
          <title>
         ISO/IEC 13818, Generic coding of moving pictures and associated
         audio information.
          </title>
          <author>
            <organization>ISO/IEC</organization>
          </author>
        </front>
      </reference>

    </references>
  </back>

</rfc>
