asterisk users - Mar 2007 - Scratchy Audio with Asterisk 1.2.4 over IAX on FreeBSD?

Hi all

We run an * 1.2.4 under FreeBSD with ztdummy kernel module.
zttest reports 99.9something % of accuracy, so timing should be fine.

SIP connections work fine, but we have a strange problem with IAX2 
connections.

When an IAX2 call originates from the FreeBSD Asterisk to another Asterisk, 
the sound is scratchy (sounds a bit like a 50Hz ground loop).

It's not a problem of the 'other' asterisk, as the problem could be
reproduced
with * 1.2.5/Linux and * 1.4.2/Linux.

If the IAX2 call originates from another * to the FreeBSD one, the sound is 
clear.

Format used is alaw. (ulaw also shows that problem, gsm doesn't work at all,
but that could be a codec problem of the 1.2.4 gsm implementation)

Playing around with the IAX jitterbuffer settings does not affect the 
scratching sound in any way.

Any idea what the cause could be?

Mit freundlichen Gr?ssen

Benoit Panizzon
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