Hi,
we recently encountered a problem with IVM Answering Attendant after our upstream sip provider disabled audio transcoding on the calls (probably due to performance problems).
The setup we are running is as follows:
SIP Provider -> Draytek 2810 IP PBX -> IVM Attendant
A normal call from a terminal connected to either the IPPBX or directly to the sip provider, and uses g711U works fine, however, an external call (eg mobile, land line) is initiated like this:
PBX -> IVM:
v=0
o=Sippy 183797232 0 IN IP4 xxx.xxx.xxx.xxx
s=VoipCall
t=0 0
m=audio 10126 RTP/AVP 8 0 18 8 18 101
c=IN IP4 192.168.41.1
a=rtpmap:8 PCMA/8000/1
a=ptime:20
a=rtpmap:0 PCMU/8000/1
a=fmtp:18 annexb=no
a=rtpmap:18 G729/8000/1
a=rtpmap:8 PCMA/8000/1
a=fmtp:18 annexb=no
a=rtpmap:18 G729/8000/1
a=rtpmap:101 telephone-event/8000/1
a=sendrecv
IVM -> PBX:
v=0
o=NCHSoftware-IVM 1318295087 1318295092 IN IP4 192.168.41.21
s=IVM Answering Attendant Call
c=IN IP4 192.168.41.21
t=0 0
m=audio 8000 RTP/AVP 0 8 101
a=rtpmap:0 PCMU/8000
a=rtpmap:8 PCMA/8000
a=rtpmap:101 telephone-event/8000
a=fmtp:101 0-16
a=sendrecv
a=direction:active
Since the uplink provider asks for g711a and receives g711u, the remote end hears nothing coming from the IVM.
Is there any way to fix this ?