[Asterisk-Users] Call between G.711 and GSM

[Dan]

Hi all,

I have a Cisco 7960 IP PHONE and an X-Lite soft phone, both connected to an
Asterisk PBX as SIP phones.
If G.711 codec is used by both phones (GSM codec disabled on X-Lite), the
sound is perfect.
When I enable GSM on X-Lite, it tends to use it for any call and then
Asterisk make a conversion between GSM and G.711 (I'm right with this
one???).
The call is established, 7960 display the used codec as G.711 and X-Lite as
GSM, but all I can hear is only a lot of noise. The music on hold feature
works ok on both sides.

How can I do to use this type of configuration?
7960 does not have GSM codec, nor G.723 and I have no G.729 on X-Lite.
I want to be able to use it where G.711 is not suitable because of the
available bandwidth.
Cisco 7960 is in the same LAN as Asterisk PBX, but X-Lite client ie
remotely, over a not so good link (but perfect for GSM codec).
Any suggestions?

Thanks,
Dan