Hi Andrew,

I'm guessing you already know that some sound card drivers allow all the audio 
output channels to be mixed into the input channel, which is either the 
Microphone on a desktop node or Line In on a room node. This is usually a 
Windows Volume Control recording setting, something like 'Stereo Mix' or 'Wave 
Out Mix'.

But I don't know how you'd prevent echo, as the incoming audio would end up in 
the same audio channel as local applications, i.e. the 'Wave' channel.

I agree that 2 sound cards is the best option, getting apps to choose their 
preferred sound device. You'd then need to physically bridge the Line Out of 
the app's sounds card into the input of the AG sound card, i.e. using a 3.5mm 
jack Tee. I'm not sure how this would work out with a desktop node, as you're 
using the Mic input on the AG sound card, i.e. different levels.

Hope I've got this right!?

Ben.



  _____

From: [email protected] [mailto:[email protected]] On Behalf Of 
Andrew Leahy
Sent: 25 August 2008 05:30
To: ag-tech
Subject: [AG-TECH] how do I get desktop audio 'into' AG/RAT?


Hi - this is a tough one because of all the echo/feedback problems.

How do sites capture audio from applications on a AG desktop and get it into 
the AG environment?

For example, if I want to share desktop multimedia I can use VPCScreenProducer 
to inject the video into VIC.
But what do I do about audio? the normal audio-out is echo cancelled by the 
ClearOne or similar device so isn't transmitted into RAT.

One idea, that I haven't tried, is to use a second sound device and feed it 
into the ClearOne or room to be picked up by the line/mic-in on the primary 
card (where RAT is recording)? But then I have the hassle of figuring how to 
tell particular apps to use device 2 rather than device 1 for audio.

My application is with Linux (FC) desktops, but the same problem would apply to 
Windows & OS X.

Any advice would be welcome.

Cheers, Andrew

School of Computing & Mathematics
University of Western Sydney


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