Author Topic: G726 not working for peer to peer calls  (Read 663 times)


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G726 not working for peer to peer calls
« on: April 11, 2017, 02:02:40 AM »

I'm using the Grandstream GXV3140 and I've noticed that there seems to be a problem with using G726 for peer to peer calls.

The scenario is that I setup the Grandstream and the receiver (an AXIS A8105-E Door Station) to only use G726 but when I do a peer to peer call (initiated from the A8105) the Grandstream will select PCMU in the SIP OK message, which will lead to no audio in the call as G726 is turned off in the A8105. This does not seem to be an issue if the call is routed through a PBX, there G726 is negotiated just fine and audio works.

So, my question is if there is a known problem with G726 for peer to peer calls and why it still selects and tries to use PCMU?

I found a similar issue in a different thread in this forum:

This is the SDP sent by the A8105 in the INVITE:

o=- 3700816416 3700816416 IN IP4
t=0 0
a=X-nat:0 Unknown
m=audio 4008 RTP/AVP 110 96
c=IN IP4
a=rtcp:4009 IN IP4
a=rtpmap:110 G726-32/8000
a=rtpmap:96 telephone-event/8000
a=fmtp:96 0-16
m=video 4010 RTP/AVP 97
c=IN IP4
a=rtcp:4011 IN IP4
a=rtpmap:97 H264/90000
a=fmtp:97 profile-level-id=42000d

And this is the SDP received from the GXV3140 in the SIP OK:

o=60051 8000 8000 IN IP4
s=SIP Call
c=IN IP4
t=0 0
m=audio 5004 RTP/AVP 96 0
a=rtpmap:96 telephone-event/8000
a=fmtp:96 0-15
a=rtpmap:0 PCMU/8000
m=video 5006 RTP/AVP 97
a=rtpmap:97 H264/90000
a=fmtp:97 profile-level-id=42000d; sprop-parameter-sets=Z0KADJWgUH5A,aM4Ecg==; max-br=128