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Source-Specific Media Attributes in Jingle This specification provides an XML mapping for translating the RFC 5766 Source-Specific Media Attributes from SDP to Jingle &LEGALNOTICE; xxxx ProtoXEP Standards Track Standards Council XEP-0166 NOT_YET_ASSIGNED 0.0.1 2013-11-25 ph

First draft.

 &fippo;

&rfc5576; provides a mechanism to describe attributes of individual media sources (identified by their synchronization source) within a media stream. A mapping to Jingle as an extension to &xep0167; is defined in this document.

The SDP format defined in RFC 5576 is shown below.

a=ssrc:<ssrc-id> <attribute> a=ssrc:<ssrc-id> <attribute>:<value>

This maps to Jingle as a <source/> element qualified by the 'urn:xmpp:jingle:apps:rtp:ssma:0' namespace. Since 'ssrc' is a media attribute in SDP, the <source/> element is included as child of the Jingle <description/> element.

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Each ssrc-id maps to a <source/> element whose 'ssrc' attribute is set to the ssrc-id. The associated attributes map to <parameter/> children with 'name' and 'value' attributes. If there is no value in the SDP, the value parameter shall be omitted.

An example follows:

a=ssrc:1656081975 cname:Yv/wvbCdsDW2Prgd a=ssrc:1656081975 msid:MLTJKIHilGn71fNQoszkQ4jlPTuS5vJyKVIv MLTJKIHilGn71fNQoszkQ4jlPTuS5vJyKVIva0 a=ssrc:1656081975 mslabel:MLTJKIHilGn71fNQoszkQ4jlPTuS5vJyKVIv a=ssrc:1656081975 label:MLTJKIHilGn71fNQoszkQ4jlPTuS5vJyKVIva0 ]]>

The SDP format defined in RFC 5576 is shown below.

a=ssrc-group:<semantics> <ssrc-id> ...

This maps to Jingle as a <ssrc-group/> element qualified by the 'urn:xmpp:jingle:apps:rtp:ssma:0' namespace. Like the <source/> element, this is included as child of the Jingle <description/> element. The SDP 'semantics' parameter is mapped to the type attribute (for consistency with FIXME jingle-grouping FIXME) and the list of ssrc-ids is mapped to <source/> elements whole 'ssrc' attribute is set to the ssrc-id.

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The following example is taken from RFC 5576.

m=video 49174 RTP/AVPF 96 98 a=rtpmap:96 H.264/90000 a=rtpmap:98 rtx/90000 a=fmtp:98 apt=96;rtx-time=3000 a=ssrc-group:FID 11111 22222 a=ssrc:11111 cname:user3@example.com a=ssrc:22222 cname:user3@example.com a=ssrc-group:FID 33333 44444 a=ssrc:33333 cname:user3@example.com a=ssrc:44444 cname:user3@example.com

This is mapped to Jingle as follows:

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If an entity supports source specific media attributes as described in RFC 5576, it MUST advertise that fact in its responses to &xep0030; information ("disco#info") requests by returning a feature of 'urn:ietf:rfc:5576':

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In order for an application to determine whether an entity supports this protocol, where possible it SHOULD use the dynamic, presence-based profile of service discovery defined in &xep0115;. However, if an application has not received entity capabilities information from an entity, it SHOULD use explicit service discovery instead.

The SDP syntax examples are taken from RFC 5576.

This document introduces no additional security considerations above and beyond those defined in the documents on which it depends.

This document requires no interaction with &IANA;.

This specification defines the following XML namespace:

  • urn:xmpp:jingle:apps:rtp:ssma:0

The ®ISTRAR; includes the foregoing namespace to the registry located at &NAMESPACES;, as described in Section 4 of &xep0053;.

 &NSVER;

TODO