One document matched: draft-nandakumar-payload-sdp-max-video-resolution-00.xml

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<rfc ipr="trust200902" category="std" docName="draft-nandakumar-payload-sdp-max-video-resolution-00"
submissionType="IETF" xml:lang="en">
<front>
    <title abbrev="Video Resolution Negotiation">
     Payload specific parameters for specifying video resolution in SDP.
	</title>
	 <author fullname="Suhas Nandakumar" initials="S." surname="Nandakumar">
      <organization>Cisco</organization>
      <address>
        <postal>
          <street>170 West Tasman Drive</street>
          <city>San Jose</city>
          <region>CA</region>
          <code>95134</code>
          <country>USA</country>
        </postal>
        <email>snandaku@cisco.com</email>
      </address>
    </author>
    <author fullname="Christer Holmberg" initials="C." surname="Holmberg">
      <organization>Ericsson</organization>
      <address>
        <postal>
        <street>Hirsalantie 11</street>
        <code>02420</code>
        <city>Jorvas</city>
        <country>Finland</country>
        </postal>
        <email>christer.holmberg@ericsson.com</email>
      </address>
    </author>

    <date year="2013" month="December" day="7" />
    <area>Transport</area>
    <workgroup>Payload Working Group</workgroup>
    <keyword>RTP</keyword>
    <keyword>SDP</keyword>
    <keyword>CLUE</keyword>
    <keyword>RTCWEB</keyword>
    <keyword>MMUSIC</keyword>

    <abstract>
	<t>
       With the rise in realtime communication applications supporting video,
       there is a need for receivers of the video to setup appropriate
       expectations on their receive capacity for handling various video
       image resolutions. Setting up the maximum supported image resolution that
       could be handled by an Endpoint is important to successfully decode and
       render the received video streams. This document proposes SDP format specific
       parameters for specifying the maximum image width and height resolutions along
       with their behavior under the <xref target="RFC3264"/> Offer/Answer SDP usage. 
     </t>
    </abstract>
</front>

<middle>
<section title="Terminology" toc="default">
		<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.
		</t>
	</section>

    <section anchor="sec.introduction" title="Introduction" toc="default">
      <t>
        Off late, multimedia communication sessions are increasingly supporting video
        by default. This is further fueled with the advent of IETF technology standards
        such as RTCWeb, CLUE. In order to successfully decode an
        incoming video stream, the decoder at the Endpoint must be capable of handling
        the image resolution of the received video streams, amongst other things.
        This document defines SDP payload format specific paramaters (a=fmtp)
        to setup an upper limit on the receiver's capability in successfully handling 
        various image resolutions of the incoming  video stream. It also describes 
        <xref target="RFC3264"/> Offer/Answer procedures for the same.
      </t>
      <t>
        Individual RTP Payload specifications that intend to specify limits on the decoder's 
        image resolution handling MUST refer to the parameters defined in this document to
        achieve the functionality.
       </t> 
    </section>

    <section anchor="sec.ptparams"  title="Payload Format Parameters" toc="default">
      <t>
       The media subtype parameters max-recv-width and max-recv-height
       specified below MAY be used to signal the capabilities of a receiver implementation.
       These parameters MUST NOT be used for any other purposes.
      </t>
      <section title="Media Type Registration" toc="default">
        <t>
          New Parameters
          <list style="numbers">
            <t> max-recv-width: The value of max-recv-width is an integer indicating
              maximum horizontal image range in pixels. When max-recv-width is
              signaled, the sender MUST NOT send any media with horizontal image 
              resolutions higher than the value requested by the receiver.
            </t>
            <t> max-recv-height: The value of max-recv-height is an integer indicating
              maximum vertical image range in pixels. When max-recv-height is
              signaled, the sender MUST NOT send any media with vertical image
              resolutions higher than the value requested by the receiver.
            </t>
          </list>
        </t>
      </section>
    </section>
    <section anchor="sec.sdp"  title="SDP Parameters" toc="default">
      <section title="Mapping of the parameters to SDP" toc="default">
        <t>
          The parameters max-recv-width, max-recv-height when present,
          MUST be included in the "a=fmtp" line of SDP. These parameters are
          expressed as a media type string, in the form of a semicolon separated
          list of parameter=value pairs.
        </t>
        <t>
          When signaled, both the attributes MUST be included and they signal the
          capabilities of a media receiver's implementation. These parameters are
          implicitly downgradable from the media sender's perspective, i.e, they
          express the upper limit for a media sender's possible behavior. Thus a media
          sender MAY select to set its encoder using only lower/lesser or equal values
          of these parameters when sending media.
        </t>
      </section>
      <section title="Usage with SDP offer/answer" toc="default">
        <t>
          The interpretation of the parameters max-recv-width and
          max-recv-height depends on the SDP direction attribute. When the
          direction is sendrecv or recvonly, the value of this parameter
          indicates the ranges of horizontal and vertical image resolutions
          the media receiver is capable of rendering successfully. When the
          direction is sendonly, these attributes have no interpretation and
          MUST be ignored by the receiving Endpoint, if present.
        </t>
        <t>
          If the media sender is not capable of sending any resolution
          lower than or equal to the values requested by the media receiver, the 
          Offer/Answer procedure is considered as failed.
        </t>
        <t>
          An SDP Answerer MUST NOT include these parameters in the SDP Answer
          unless they are specified in the associated SDP Offer.
        </t>
        <t>
          If the SDP Answer doesn't contain these parameters, the Offerer MUST
          follow the procedures in the same way as if these parameters were never
          sent in the first place. This might happen if the Answerer doesn't
          support/understand these parameters.
        </t>
      </section>
    </section>
    <section anchor="sec.examples" title="SDP Examples" toc="default">
      <section title="Successful Scenario" toc="default">
        <t>
          The example SDP below shows an Offer from an Endpoint that is capable of
          receiving up to [720,576] video image resolution for the VP8 codec
          with Payload Type 96.
        </t>
        <figure title="SDP Offer">
        <artwork><![CDATA[
m=video 62537 RTP/SAVPF 96
a=rtpmap:96 VP8/90000
a=fmtp:96 max-fr=30;max-recv-width=720;max-recv-height=576
a=sendrecv
]]></artwork>
      </figure>
        <t>
          The example SDP below shows an Answer from an Endpoint that is  capable of 
          receiving only up to [640,480] video image resolutions.
        </t>
        <figure title="SDP Answer">
        <artwork><![CDATA[
m=video 62537 RTP/SAVPF 96
a=rtpmap:96 VP8/90000
a=fmtp:96 max-fr=30;max-recv-width=640;max-recv-height=480
a=sendrecv
]]></artwork>
        </figure>
      </section>
       <section title="Failure Scenario" toc="default">
        <t>
          The example SDP below shows an Offer from an Endpoint that is capable of
          receiving up to [720,576] video image resolution for the H.264 codec
          with Payload Type 100.
        </t>
        <figure title="SDP Offer">
        <artwork><![CDATA[
m=video 62537 RTP/SAVPF 100
a=rtpmap:100 H264/90000
a=fmtp:100
  profile-level-id=42800d;max-mbps=40500;max-recv-width=720;max-recv-height=576
a=sendrecv
]]></artwork>
       </figure>
        <t>
          The example SDP below shows the Answer rejecting the above SDP Offer,
          since the receiver of the SDP is unable to support the Offerer's requested 
          image resolutions for sending the media.
        </t>
        <figure title="SDP Answer">
         <artwork><![CDATA[
m=video 0 RTP/SAVPF 100
a=rtpmap:100 H264/90000
]]></artwork>
        </figure>
      </section>
    </section>
	  <section anchor="sec.iana" title="IANA Considerations" toc="default">
		<t>
      The parameters specified in <xref target="sec.ptparams"/>
      of this document will be registered with the IANA.
		</t>
    </section>
    <section anchor="sec.acks" title="Acknowledgements" toc="default">
       <t>
         The authors would like to thanks Cullen Jennings, Ali C. Began,
         Harald Alvestrand and Roni Evens for their review and valuable
         comments.
       </t>
    </section>
</middle>

<back>
    <references title="Normative References">

     <reference anchor="RFC3264">
        <front>
          <title>An Offer/Answer Model with Session Description Protocol
            (SDP)</title>

          <author fullname="J. Rosenberg" initials="J." surname="Rosenberg">
            <organization></organization>
          </author>

          <author fullname="H. Schulzrinne" initials="H."
            surname="Schulzrinne">
            <organization></organization>
          </author>

          <date month="June" year="2002" />
        </front>

        <seriesInfo name="RFC" value="3264" />

        <format octets="60854"
          target="http://www.rfc-editor.org/rfc/rfc3264.txt" type="TXT"/>
        </reference>
      <reference anchor="RFC4566">
        <front>
          <title>SDP: Session Description Protocol</title>

          <author fullname="M. Handley" initials="M." surname="Handley">
            <organization></organization>
          </author>

          <author fullname="V. Jacobson" initials="V."
            surname="Jacobson">
            <organization></organization>
          </author>

          <author fullname="C. Perkins" initials="C."
            surname="Perkins">
            <organization></organization>
          </author>

          <date month="July" year="2006" />
        </front>

        <seriesInfo name="RFC" value="4566" />

        <format octets="60854"
          target="http://http://tools.ietf.org/html/rfc4566.txt" type="TXT" />
      </reference>
    </references>

  </back>
</rfc>