[Asterisk-Users] Faxdetection in IAX? (Missing audio samples)

[Roger Schreiter]

Hi,

please don't bother me continuing trying to fax, even if
I've got convinced, that it generally won't work!

I've found a strange behaviour, when sending
from IAXCLIENT1 -> asterisk -> IAXCLIENT2
or
from IAXCLIENT1 -> asterisk -> SIPCLIENT2

When IAXCLIENT1 is sending an absolutely constant
frequence (fax detection tones at the very beginning of
every fax session), audio samples get cleared (set to 0).

I dumped both, the outgoing samples from IAXCLIENT1
and incoming from IAXCLIENT2, respectively heard by myself with
a SIP phone.

IAXCLIENT1 sending a constant tone of exactly 3000 msec,
which leads in the dump file to a very periodic pattern
of hex numbers, and thus is easy to find "manually" in the dump file.

Arriving at IAXCLIENT2 respectively at the SIP phone is
that tone for exactly 500 msec, afterwords silence for
approx 2450 msec.


Is there an explanation for this behaviour?

Thanks for any hints!
Roger.