A UA indicates it doesn't support one or more of the media formats received in an offer by omitting the payload type(s) not supported in its answer (see section 6.1 in rfc3264). It rejects a media type by setting the port number to zero (see section 8.2 in rfc3264). So for your example, the offer will contain a media line in its SDP as:
m=audio 23456 RTP/AVP 96 97
...
m=video 23556 RTP/AVP 98
where "a=" lines (appearing after the corresponding "m=" line) map 96 & 97 to the G.723 & G.729 media formats and map 98 to the H.263 media format. The answerer will formulate its answer with media lines in its SDP as:
m=audio 33222 RTP/AVP 96 99
...
m=video 0 RTP/AVP 98
where "a=" lines map 96 & 99 to the G.723 & g.711 media formats.
Regards,
Bert
Prasanna Venkatesh wrote:
Hi Jade, This should be taken care by the offer - answer model. The error code for INVITE is 488. There can be a body in the 488 mentioning the media capabilities supported. But there are issues as the 488 is hop-by-hop it can be dropped. I am also not sure how to just denote the capabilities in the SDP.Regards, Prasanna -----Original Message----- From: Jade Chen Yan [mailto:[EMAIL PROTECTED]] Sent: Thursday, January 23, 2003 2:23 PM To: 'Prasanna Venkatesh' Subject: RE: [Sip-implementors] accept header thank u for your reply. But if the one UA cannot accept the media type eg , G.729 , it support the G.711 & g.723, how can the UA tell the other party,?which header should be used? the UA generate a 481 responsed which contains the sdp body? regards, Jade -----Original Message----- From: Prasanna Venkatesh [mailto:[EMAIL PROTECTED]] Sent: Thursday, January 23, 2003 4:43 PM To: jade(3???) Subject: RE: [Sip-implementors] accept header Accept is for the SIP bodies and not the media which is defined by the bodies. An example is Accept: application/sdp, text/*, image/gif The media codecs(g.729 / g.723 etc.) are defined by the sdp body. -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Jade Chen Yan Sent: Thursday, January 23, 2003 1:45 PM To: Sip-Implementors (E-mail) Subject: [Sip-implementors] accept header hi, list, Can any one give me an example for the accept header?eg, the ua accept the g.723, g.729 & h.263 codec. thanks. Best Regards, Jade _______________________________________________ Sip-implementors mailing list [EMAIL PROTECTED] http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors _______________________________________________ Sip-implementors mailing list [EMAIL PROTECTED] http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
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