[Freeswitch-users] SDP with 2 m=audio lines

Sergey Okhapkin sos at sokhapkin.dyndns.org
Tue Feb 14 16:39:24 MSK 2012


I noticed that recent freeswitch versions could send SDP with 2 m=audio lines. 
Per RFC 3388, the behavior is undefined this case. I don't know how to 
reproduce the problem, I see such packets coming from my customers. Here is an 
example:

INVITE sip:xxxxxxxxxxxx at sip.callwithus.com SIP/2.0
...
User-Agent: FreeSWITCH-mod_sofia/1.0.head-git-eeeaf41 2012-02-10 17-27-50 -0600
....

v=0
o=FreeSWITCH 1329167961 1329167962 IN IP4 xx.xx.xx.xx
s=FreeSWITCH
c=IN IP4 xx.xx.xx.xx
t=0 0
m=audio 24598 RTP/AVP 0 101 13
a=rtpmap:101 telephone-event/8000
a=fmtp:101 0-16
a=ptime:30
m=audio 24598 RTP/AVP 98 0 8 3 101 13
a=rtpmap:98 SILK/8000
a=fmtp:98 useinbandfec=1; usedtx=0
a=rtpmap:101 telephone-event/8000
a=fmtp:101 0-16
a=ptime:20


Hmm, I just realized that this SDP is buggy - 2 audio streams on the same 
port, with common codecs, but with different ptime :-)



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