I have only just started using pjsua from the command line and have difficulties understanding the the last bit of the log output for sip:music at iptel.org that plays music. Log extracts: Make call: sip:music at iptel.org 17:35:23.976?? pjsua_call.c? Making call with acc #1 to sip:music at iptel.org OFFER: >>>INVITE sip:music at iptel.org SIP/2.0 ... m=audio 40000 RTP/AVP 98 97 99 104 3 0 8 9 96 c=IN IP4 192.168.0.2 a=rtcp:40001 IN IP4 192.168.0.2 a=sendrecv a=rtpmap:98 speex/16000 a=rtpmap:97 speex/8000 a=rtpmap:99 speex/32000 a=rtpmap:104 iLBC/8000 a=fmtp:104 mode=30 a=rtpmap:3 GSM/8000 a=rtpmap:0 PCMU/8000 a=rtpmap:8 PCMA/8000 a=rtpmap:9 G722/8000 a=rtpmap:96 telephone-event/8000 a=fmtp:96 0-15 <<< INVITE 100 Trying... ANSWER: <<< INVITE 200 response ... m=audio 28108 RTP/AVP 97 104 3 0 8 96 a=rtpmap:97 speex/8000 a=rtpmap:104 iLBC/8000 a=fmtp:104 mode=30 a=rtpmap:3 GSM/8000 a=rtpmap:0 PCMU/8000 a=rtpmap:8 PCMA/8000 a=rtpmap:96 telephone-event/8000 a=fmtp:96 0-15 >>>ACK sip:music at 217.9.36.144:5080 SIP/2.0 Respondent wants speex/8000 the second item in the choice list of the offer. I don't understand why the offerer continues with the negotiation?: OFFER: >>>INVITE sip:music at 217.9.36.144:5080 SIP/2.0 m=audio 40000 RTP/AVP 97 96 c=IN IP4 192.168.0.2 a=rtcp:40001 IN IP4 192.168.0.2 a=sendrecv a=rtpmap:97 speex/8000 a=rtpmap:96 telephone-event/8000 a=fmtp:96 0-15 <<<INVITE 100 trying ANSWER: <<<INVITE 200 response ... m=audio 28108 RTP/AVP 97 96 a=rtpmap:97 speex/8000 a=rtpmap:96 telephone-event/8000 a=fmtp:96 0-15 I read RFC3264 - An Offer/Answer Model with the Session Description Protocol (SDP), but could not see an explanation for this continued negotiation. Maybe I misunderstood the RFC. I would like to understand this a bit better... Guidance most welcome. Ken -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.pjsip.org/pipermail/pjsip_lists.pjsip.org/attachments/20120304/44ba6394/attachment.html>
