Is it allowed to map a different codec to particular dynamic payload number in the SDP answer than in the SDP offer? I think RFC 3264 is unclear on this.
For example if an endpoint A sends an SDP offer like this: m=audio 10001 RTP/AVP 8 119 a=rtpmap:8 PCMA/8000 a=rtpmap:119 FooBar/8000 Is B then allowed to answer with and SDP like this? m=audio 10001 RTP/AVP 8 119 a=rtpmap:8 pcma/8000 a=rtpmap:119 telephone-event/8000 page 10 in RFC 3264: "In the case of RTP, if a particular codec was referenced with a specific payload type number in the offer, that same payload type number SHOULD be used for that codec in the answer." The "SHOULD" doesn't explicitly forbid anyone from using the same payload type number for a different codec in the SDP answer. page 15 RFC 3264: "However, in the case of RTP, the mapping from a particular dynamic payload type number to a particular codec within that media stream MUST NOT change for the duration of a session. For example, if A generates an offer with G.711 assigned to dynamic payload type number 46, payload type number 46 MUST refer to G.711 from that point forward in any offers or answers for that media stream within the session." This part seems to forbid the reuse of payload type numbers for different codecs, but is located in "8.3.2 Changing the Set of Media Formats". I really need to know if reusing dynamic payload numbers in SDP answers is ok or not? / Christian Jansson _______________________________________________ Sip-implementors mailing list [EMAIL PROTECTED] http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
