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Date:      Thu, 04 Apr 2002 11:55:53 -0800
From:      Lars Eggert <larse@ISI.EDU>
To:        The Anarcat <anarcat@anarcat.dyndns.org>
Cc:        John Utz <john@utzweb.net>, multimedia@FreeBSD.ORG
Subject:   Re: Soundblaster Live rear channels?
Message-ID:  <3CACAFC9.3060908@isi.edu>
References:  <3CAC8E70.3040700@isi.edu> <Pine.LNX.4.44.0204041147440.2292-100000@jupiter.linuxengine.net> <20020404193214.GD279@lenny.anarcat.dyndns.org> <3CACAC92.3040506@isi.edu> <20020404194937.GE279@lenny.anarcat.dyndns.org>

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The Anarcat wrote:
 >> My understanding was that "virtual" channels act like virtual sound
 >> cards, i.e. each applications gets what looks like a separate
 >> sound device, and the kernel muxes the output. I'm not sure this
 >> has anything to do with the mixer channels, which is where I would
 >> expect the rear channel to show up.
 >
 >
 > And this is why I brought up the "mapping" issue. I think pcm can use
 > the multiple channels available (front and rear) through the virtual
 > channels technique.
 >
 > The kernel can mux the input from various apps into a single sound
channel,
 > so it's likely that it can do the opposite: mux a single sound input
 > to multiple channels.
 >
 > I can't answer wether it is the case, but it's likely to be.

It's not as simple as that. There's harware on the card that processes
stereo input (from apps) and creates four separate signals for surround
sound. (Otherwise you could simply hook up the rear speaker pair in 
parallel to the front one, using the same output signals.)

Lars
-- 
Lars Eggert <larse@isi.edu>               Information Sciences Institute
http://www.isi.edu/larse/              University of Southern California

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