6 Dec
2004
6 Dec
'04
9:21 a.m.
On Dec 04, 2004 at 19:27, Java Rockx <javarockx(a)yahoo.com> wrote:
Hi All.
I got the thinking about this and now I'm not so sure it's as easy as I once
thought.
At what point in SER do we actually know which CODEC the caller has finally chosen? I
mean if
CallerA sends an original INVITE to CalleeB and SDP payload of
m=audio 1234 RTP/AVP 97 101
a={iLBC}
a={G729}
a={GSM}
a={ULAW}
and CalleeB replies with 200 OK and the following SDP
m=audio 54324 RTP/AVP 18 101
a={G729}
a={ULAW}
a={speex}
a={iLBC}
Is there anyway to know which CODEC CallerA will really begin sending RTP with? The way
RFC3261
reads to me is that CallerA is not obligated to honor G729 as stated in the "200
OK" from CalleeB
because the RFC says that CallerA *SHOULD* use G729 but may use any CODEC common to both
parties.
The only way is to catch the rtp and match the codec no. with the
codec numbers advertised in the sip messages.
Andrei