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[Peter DeSantis]

Hi,

i have an audio problem on an access grid, if anyone can please help

This is a 3 pc access grid, that works fine, except for an unresolvable audio feedback problem.

The audio capture computer is

Intel P4 3.2Ghz
Xp pro SP2
Soundblaster Audigy2 soundcard.
Vortex EF4220 echo canceler.

Basicly, we set up the grid, ran all the software, adjusted the echocanceer and everything was fine for 3 days.  We had regular test conversations with other users and except for a minor feedback and echo issue that were quickly fixed everything was perfect as far as we could see.  Basically for 3 days audio seem totaly great.

Normaly the pcs are left on, then one morning we noticed the audio capture computer had reset for some reason and was sitting at the bios screen. We resarted it and all seemed fine untill we ran the AG software for a session.

Basicly the problem is there is now this intense unexplained feedback loop occuring, where before there was none.  Using the echo canceler software we can monitor the audio levels in the echo canceler and the diagnostic screens show maxed out levels of internal audio running through it.  Previously the levels were normal.  

When we restart the computer and echo canceler the internal audio levels look normal.  Then when we start the AG software and the RAT runs, we can see on the dignostic screen the internal audio levels get maxed out, BUT no feedback is audiable in the room through the hardware and no problem noise is audiable to the other end.  But then if we exit the RAT client the feedback screams out the speakers into the room and we have to shut the amp off to quiet it, to prevent damage.  this is the strange thing that the feed back only comes out the speakers when the rat is shut off, and we also get it when the RAT shuts down briefly to change from one room to the next.

For 3 days the system worked fine then suddenly this started and i cant figure whats causing it, as every setting on the echo cancler and the sound card is the same as before.  We made sure the "record without monitoring" option on the sound card was activated as this was the initial casue of feedback that stoped when we activated it.  I am totaly flabergasted as to what the casue might be.  Its almost as if the RAT client is bridging some internal soundcard buffer when it runs, causing audio sources to be mixed and casuing the problem.  As i said, it all ran fine for 3 days before this quirk started.


Has anyone had anything similar ?  It occurs to me perhaps the best thing to try might be to reinstall XP and AG toolkit from scratch.

Any help appreciated.
 
Thanks

Peter DeSantis
peter at jumbovision.com.au
Jumbo Vision International Pty Ltd
Unit 2 ,1 Aitken Way
Kewdale WA 6105
Australia

Tel: 61 8 9353 6200
Fax: 61 8 9353 6211