asterisk users - Nov 2006 - MS-GSM codec issues - Anybody seen anything similar?

All,

Has anybody come across a problem with the MS-GSM codec on Asterisk?  We 
have a client for Windows XP that uses the MS-GSM codec.  While the 
codec seems to work when talking directly to Asterisk, when 2 of these 
clients talk to each other through Asterisk the sound is all mangled on 
both ends.  I assume MS-GSM is the same as used by Windows Messenger and 
so my problem may be related to an earlier posting which had no replies:

http://www.archivum.info/asterisk-users@lists.digium.com/2006-01/msg00988.html

We are running v1.2.13 and we have tried v1.4.0-beta3 too. 
Interestingly, on v1.4 the codec shows up as 'unknown' when you look at 
the call using 'sip show channels'?  If anybody has heard of similar 
issues let me know.

Kind of related to this, is it possible with Asterisk to do GSM 
pass-through?  i.e. Have Asterisk act as an RTP proxy and pass the RTP 
between clients with no interference?  This could also be an option 
since the clients talk GSM fine to each other is seems.

Cheers,
Ray

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