[asterisk-users] "clicking" sound with alaw codec

[Richard Kenner]

I'm trying to interface Asterisk with an Alcatel PABX and trying to find
a code that works well.  It says it doesn't support ulaw, though it
doesn't reject it.  It supports G.729, and that works fine, but we'd prefer
not to use compression.

When I use alaw, the path from Asterisk to the Alcatel is completely
clean, but the other way has a set of clicks that kind of sound like
old-fashioned audio noise.

The outgoing SDP looks like this:

v=0
o=root 1691755711 1691755711 IN IP4 205.232.38.178
s=Asterisk PBX 10.7.1
c=IN IP4 205.232.38.178
t=0 0
m=audio 11432 RTP/AVP 8 101
a=rtpmap:8 PCMA/8000
a=rtpmap:101 telephone-event/8000
a=fmtp:101 0-16
a=ptime:20
a=sendrecv

The reply SDP is:

v=0
o=default 1359060187 1359060187 IN IP4 10.10.22.246
s=Asterisk PBX 10.7.1
c=IN IP4 10.10.22.246
t=0 0
m=audio 32000 RTP/AVP 8 101
a=sendrecv
a=rtpmap:101 telephone-event/8000
a=fmtp:101 0-15
a=ptime:20
a=maxptime:90

Any suggestions on how to debug what's causing this?