asterisk users - Nov 2009 - Asterisk with H323 channel and Gnugk: no voice

Hi All;

I am trying to have the possibility to pass traffic from SIP to H323, and I am
using the asterisk version 1.4.26.2 with h323 (so I have h323.so channel), the
h323 listens at port 1722 TCP and on the same machine I have gnugk running and
listens on 1721 TCP.

When placing a call from the SIP phone registered to Asterisk and trying to
reach an H323 Phone register to gnugk, then the call reachs to the H323 Phone,
and when they answer no voice (we do not hear any thing).

What could be the problem? Do I have to try oh323 instead of h323 that come with
asterisk? Or I have to run the gnugk on another IP address than the asterisk is
running?

Any advise solution for this problem?

Regards
Bilal