Let us say A makes an SDP offer which looks like
m=audio 49120 RTP <http://www.voip-telephony.org/rfc/avt> /AVP 97 a=rtpmap:97 EVRC/8000 a=fmtp:97 maxinterleave=2 m=video 49170/2 RTP/AVP 98 a=rtpmap:98 MP4V-ES/90000 a=fmtp:98 profile-level-id=1;config=XYZ My understanding is that these fmtp parameters are specific to the UA and not to the session; however I have a colleague who claims that these are properties of the session i.e. for a sendrecv channel both UAs must use the same fmtp values so for e.g. B which receives this offer must also use maxinterleave of 2, etc. But, I think maxinterleave is a property of the UA and need not be the same for both A and B. Same thing with the MP4 vol header which is an encoder property and hence need not be the same for both end points in a one-to-one session. So I believe this is a valid SDP answer to the above offer m=audio 49120 RTP <http://www.voip-telephony.org/rfc/avt> /AVP 97 a=rtpmap:97 EVRC/8000 a=fmtp:97 maxinterleave=5 m=video 49170/2 RTP/AVP 98 a=rtpmap:98 MP4V-ES/90000 a=fmtp:98 profile-level-id=1;config=ABC Per my colleague, the above is not a valid SDP answer to the offer. The RFCs seem very vague about the interpretation of these fmtp parameters. Is this not a source of interop nightmares where vendor implementations depend on their interpretation of these ambiguous specs or am I missing something fundamental here? Your input is most appreciated. Thanks, -Ravi. _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
