Hi, 

I have searched the list, but I couldn't find a final answer for this case. I'm receiving calls from a provider using G729 annex B. 

INVITE
a=rtpmap:18 G729/8000.
a=fmtp:18 annexb=yes.
a=rtpmap:0 PCMU/8000.
a=rtpmap:8 PCMA/8000.
a=rtpmap:101 telephone-event/8000.
a=fmtp:101 0-16.
a=rtpmap:19 CN/8000.

and FS is answering 

200OK
m=audio 31388 RTP/AVP 18 101 19.
a=rtpmap:18 G729/8000.
a=fmtp:18 annexb=yes.
a=rtpmap:101 telephone-event/8000.
a=fmtp:101 0-16.
a=rtpmap:19 CN/8000.
a=ptime:20.

If freeswitch  supports  only G729A, shouldn't FS refuse the call with 488 or suppress the line annexb=yes?

The audio quality is really bad when I receive calls in this way. After removing the annexb on the gateway the audio is fine, but unfortunately I can't remove from it from all VoIP providers terminating calls. For outbound calls I simply removed the annexb, but for inbound there is no way to do it. 

Flavio