Not sure if this is the right location to post this question; if not, my apologies to you all.
I have a problem with interpreting RFC 3264 and rfc 4566. Specifically, what is the meaning of recvonly and sendonly in the SDP of an offer. When I send an INVITE with a SDP signalling two sets of mediastreams, one set indicating my encoding capabilities, the other indicating my decoding capabilities, I would generate an SDP like the following (specific stream attributes omitted for readability): SDP: v=0 o=- 10668468788867098624 10668468788867098624 IN IP4 10.0.0.58 s=VirCom-session c=IN IP4 10.0.0.58 t=0 0 m=video 1338 RTP/AVP 34 32 a=recvonly a=rtpmap:32 MPV/90000 a=rtpmap:34 H263/90000 m=audio 1340 RTP/AVP 14 0 96 a=recvonly a=rtpmap:14 MPA/90000 a=rtpmap:0 PCMU/8000 a=rtpmap:96 G726-32/8000 m=video 1342 RTP/AVP 32 34 33 a=sendonly a=rtpmap:32 MPV/90000 a=rtpmap:34 H263/90000 m=audio 1344 RTP/AVP 14 0 a=sendonly a=rtpmap:14 MPA/90000 a=rtpmap:0 PCMU/8000 What I hope to achieve is telling my counterpart that I wish to recieve MPEG2 video or H.263 video on port 1338, and MPEG audio or mu-law audio on port 1340, and will sent video and audio on port 1342 and 1344 respectively. The IP phone I tested this with (a Grandstream GXV 3000) responded with the following (again, stream attributes omitted): v=0 o=system 8000 8000 IN IP4 10.0.0.150 s=SIP Call c=IN IP4 10.0.0.150 t=0 0 m=audio 5004 RTP/AVP 0 a=sendrecv a=rtpmap:0 PCMU/8000 m=video 5006 RTP/AVP 34 a=sendrecv a=rtpmap:34 H263/90000 To me, this seemed to indicate it wished to sent audio from port 5004, and also recieve it there, and to receive and sent video on port 5006. I assumed it would sent audio and video to my ports 1338 and 1340, but instead it uses port 1342 and 1344! The question is, how should I interpret recvonly and sendonly. Do these attributes indicate MY side of the dialog, or do they indicate the connection information I expect from my counterpart? Or is this dependent on which RFC is followed (ie RFC 4566 or rfc3264), and is it possible to signal this difference in some kind of version string in the INVITE or OK messages? With regards, Stephane van Hardeveld _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
