From mboxrd@z Thu Jan  1 00:00:00 1970
From: Takashi Iwai <tiwai@suse.de>
Subject: Re: [Alsa-user] copy pcm plugin
Date: Wed, 28 Jan 2004 18:37:32 +0100
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To: Florian Schmidt <mista.tapas@gmx.net>
Cc: alsa-user@lists.sourceforge.net, alsa-devel@lists.sourceforge.net
List-Id: alsa-devel@alsa-project.org

At Wed, 28 Jan 2004 18:05:46 +0100,
Florian Schmidt wrote:
> 
> 
> Hi, as far as i understand it, the copy plugin does nothing but copy its
> input to its output. I wonder if it would be easily possible to extend
> this plugin to copy to multiple slave pcms. This way it would be
> (easily?) possible to "distribute" a stereo signal to 4 or even 6
> channels.

route (and plug) plugin already can do that.
for example,

pcm.ch40dup {
	type route
	slave.pcm surround40
	slave.channels 4
	ttable.0.0 1
	ttable.1.1 1
	ttable.0.2 1
	ttable.1.3 1
}

pcm.ch51dup {
	type route
	slave.pcm surround51
	slave.channels 6
	ttable.0.0 1
	ttable.1.1 1
	ttable.0.2 1
	ttable.1.3 1
	ttable.0.4 0.5
	ttable.1.4 0.5
	ttable.0.5 0.5
	ttable.1.5 0.5
}


and you can play two channel WAV like

	% aplay -Dch40dup 2ch-stereo.wav

	% aplay -Dch51dup 2ch-stereo.wav

for 4.0 and 5.1 surrounds, respectively.
of course, this is just copy of left/right samples, no dolby prologic 
effect is included ;)


Takashi


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