[Asterisk-Users] Zap X100P oscillation

[Whisker, Peter]

What is particularly weird is that if I connect a call to Echo on my local
server, I don;t usually get this oscillation, however if I connect it to
Echo on another Asterisk server (over IAX), it does happen. The main
difference will be the delay in the echo, as the software versions are
within the last two days.

The Echo application is the same on both, and the call should be entirely
digital so there should be no gain differences and there is no echo
suppression on the IAX link, so it must be the local Zap echo canceller
fighting with the apparently "longer" line?

Peter


-----Original Message-----
From: Mike Benoit [mailto:ipso at snappymail.ca]
Sent: 28 June 2004 21:59
To: asterisk-users at lists.digium.com
Subject: Re: [Asterisk-Users] Zap X100P oscillation


I wonder if your issue and mine are related somehow. 

I have a asterisk server with 4 FXO cards in it, and when a call comes
in one ZAP channel, then dials out another, I hear what could be
described as a steam engine starting up. It starts off kinda slower/
quiet, then quickly (in about 2-4 seconds) completely over powers the
line. 

The only way I could stop it was by adjusting the gains.

rxgain=-8.5
txgain=4

Seemed to do the trick. As did:

rxgain=-6.5
txgain=1

An rxgain of even -8.0 or -6.0 in either case would result in this
"steam engine" sound. -8.5 or -6.5 would make it go away completely.

I'm using a CVS checkout from yesterday, and I tried with both
echotraining=800 and turning echo cancellation off completely. Neither
made any difference.

It would be really nice to be able to use a positive rxgain value. I
haven't tried with the echo app, but using just one FXO card works fine
with almost any rx/txgain value. As soon as the call utilizes two FXO
card at the same time, the "steam engine" sound occurs.


On Mon, 2004-06-28 at 16:26 +0100, Whisker, Peter wrote:
> Has anyone seen this problem before?
> 
> I have a server with a single X100P card. The audio level is a low, but if
I
> raise the gain to more than -2db (Rx + Tx) it starts to oscillate in an
echo
> test. Not at a high frequency but with a noise that is best described as a
> steam engine starting up. It then starts to clip and crackle. If I bring
the
> gain down to Rx=-2.0 and Tx=0.0 or lower then it settles down but it is
very
> very quiet.
> 
> I have tried the latest CVS Head with echotraining=800 set and also
complied
> with the aggressive echo cancelling, but nothing seems to help.
> 
> Ideas welcome!
> 
> Many thanks
> Peter Whisker
> 
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Mike Benoit <ipso at snappymail.ca>

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