[asterisk-users] odd sound between SIP & IAX clients

[Joseph Love]

The issue which occurs is that the audio from the SIP client to the  
IAX client will spend most of it's time sounded very robotic, and  
garbled.  It is possible, although very difficult to understand  
someone who is on the SIP phone.

I have asterisk 1.2.10 configured with realtime with both IAX and SIP  
clients.
The SIP clients include a Grandstream gxp2000 hard phone, and  
Counterpath's X-Lite 3 (for windows) softphone.
The IAX clients tested include idefisk (both windows & mac),  
JakenIAX, and LoudHush.
GSM is the preferred codec of both IAX & SIP clients, and is indeed  
the codec being used in all tests.

Audio from the IAX to the SIP client does not experience any issues.   
SIP to SIP (and presumably, although untested, IAX to IAX)  
communication does not experience any issues.

We also have a T1 card through which many calls have been placed,  
both from the IAX and SIP phones, without any audio issues occurring,  
in either case.

If it weren't for that there have been multiple clients tested to  
verify this robotic sound, I would cough it up to it being a  
incompatability between the particular clients, but this occurs on  
all SIP-IAX communication that has been tried.

I'm running out of options as SIP-IAX intercommunication is kinda  
expected (and necessary for me), and out of good softphones for the  
mac, as most of the mac-compatible softphones are IAX2-based.

Please let me know what additional information is needed to help me  
debug this problem.

Thanks,
-Joe