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Date:      Thu, 4 Apr 2002 14:49:37 -0500
From:      The Anarcat <anarcat@anarcat.dyndns.org>
To:        Lars Eggert <larse@ISI.EDU>
Cc:        John Utz <john@utzweb.net>, multimedia@FreeBSD.ORG
Subject:   Re: Soundblaster Live rear channels?
Message-ID:  <20020404194937.GE279@lenny.anarcat.dyndns.org>
In-Reply-To: <3CACAC92.3040506@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>

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On Thu Apr 04, 2002 at 11:42:10AM -0800, Lars Eggert wrote:
> The Anarcat wrote:
> >FreeBSD Audio Driver (newpcm) Mar 27 2002 12:56:06
> >Installed devices:
> >pcm0: <Creative EMU10K1> at io 0x9000 irq 5 (4p/1r/0v channels duplex)
> >
> >So it has 4 play channels. newpcm supports multiple through the use of
> >multiple channels, AFAIK. On -stable, newpcm supports this through
> >hw.snd.pcm0.vchans. The default value is 0 which means there is only
> >one virtual channel available. If you bump this to 1 or 2, you have
> >more virtual channels available. These are accessible through
> >/dev/dspX.Y where Y is the virtual channel.
>=20
> I think I was unclear here when using "channel".

Yes.

> What I'm trying to do=20
> is getting sound out of the two rear speakers with a 5-speaker setup.=20
> There's two separate cables that go from the soundcard to the speakers,=
=20
> one is for the front pair and subwoofer, the other drives the two rear=20
> speakers. No signal comes out of the latter.
>=20
> My understanding was that "virtual" channels act like virtual sound=20
> cards, i.e. each applications gets what looks like a separate sound=20
> device, and the kernel muxes the output. I'm not sure this has anything=
=20
> to do with the mixer channels, which is where I would expect the rear=20
> 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.

Cameron Grant <gandalf@vilnya.demon.co.uk> would be the one to answer
that, I think.

A.

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