[AG-TECH] unexplainable audio feedback problem on XP with RAT

Natalia Costas Lago natalia at cesga.es
Tue Apr 26 03:02:23 CDT 2005



R u sure your PCaudio mixer settings are correct?

----- Original Message ----- 
From: "Peter DeSantis" <peter at jumbovision.com.au>
To: <ag-tech at mcs.anl.gov>
Sent: Tuesday, April 26, 2005 9:46 AM
Subject: [AG-TECH] unexplainable audio feedback problem on XP with RAT


> 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
>
>
>
> 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
>
> 




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