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SDP Attribute for Qualifying Media Formats with Generic Parameters (gpmd)

SDP Attribute for Qualifying Media Formats with Generic Parameters (gpmd). draft-rajeshkumar-mmusic-gpmd-02.txt 56th IETF – March 17, 2003 Rajesh Kumar (rkumar@cisco.com) Flemming Andreasen (fandreas@cisco.com). Recap.

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SDP Attribute for Qualifying Media Formats with Generic Parameters (gpmd)

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  1. SDP Attribute for Qualifying Media Formats with Generic Parameters(gpmd) draft-rajeshkumar-mmusic-gpmd-02.txt 56th IETF – March 17, 2003 Rajesh Kumar (rkumar@cisco.com) Flemming Andreasen (fandreas@cisco.com)

  2. Recap • Definition of new media formats can define media format parameters to qualify the media format (fmtp). • Want to be able to define new media format parameters that can apply to existing media formats. • The “gpmd” attribute is a new SDP attribute that defines a way of specifying new optional media format parameters on a per media format basis. • Support for gpmd parameters must be optional - a hint. • Lack of receiver support for such parameters should not render the media received useless - rather an optimization. • Offer/answer can be used to determine if other side supports it and hence whether optimization can be used.

  3. Voice-Band Data • Draft defines a new gpmd parameter: • Voice-Band Data (“vbd”). • Example: m=audio 3456 RTP/AVP 0 15 98 a=rtpmap:98 PCMU/8000 a=gpmd:98 vbd=yes

  4. Changes since -01 • Firmed up definition of gpmd attribute: • gpmd attributes MUST be informative in nature. • Support for gpmd attributes MUST be optional. • Lack of support for a gpmd parameter MUST NOT render the media format in question useless: • If one side does not support a given gpmd attribute, the media format in question must still work at least as well as if the gpmd parameter had been omitted in the first place. • Normal codec negotiation (offer/answer) thus works as usual.

  5. Changes since -01 • Usage with Offer/Answer has been formally defined leading to two types of gpmd parameters: • Unilateral • Use of the parameter is not negotiated. • Each side can advertise and use it independently. • Bilateral: • Use of the parameter must be negotiated. • Can only be used if present in both offer/answer.

  6. Changes since -01 • Added section comparing “gpmd” with “fmtp”. • Added formal procedures for defining and registering new gpmd parameters: • Must be Standards-Track RFC. • Updated definition and registration of voice-band data (“vbd”) gpmd parameter in accordance with other draft changes.

  7. Next Steps • All known issues have been addressed in the current draft - any new issues ?

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