copy pcm plugin

copy pcm plugin

[Florian Schmidt]

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.

Any thoughts? Maybe i just misunderstood the pcm copy docs though..

Flo

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Re: [Alsa-user] copy pcm plugin

[Takashi Iwai]

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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Re: [Alsa-devel] Re: copy pcm plugin

[Takashi Iwai]

At Wed, 28 Jan 2004 18:37:32 +0100,
I wrote:
> 
> 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,

ah, in your question, multiple slave pcms are assumed.
in such a case, combine the multiple pcms via multi plugin at first,
then use route plugin over it.


Takashi


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Re: [Alsa-devel] Re: copy pcm plugin

[Florian Schmidt]

On Wed, 28 Jan 2004 20:02:03 +0100
Takashi Iwai <tiwai@suse.de> wrote:

> At Wed, 28 Jan 2004 18:37:32 +0100,
> I wrote:
> > 
> > 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,
> 
> ah, in your question, multiple slave pcms are assumed.
> in such a case, combine the multiple pcms via multi plugin at first,
> then use route plugin over it.

Well, i thought i would need to somehow copy to front/rear, etc,
manually. But just using the surround51 or surround40 as slave pcm
sounds just as good. Thanks, Takashi and Jaroslav for the quick infos :)
I will add them to the wiki soon..

Flo

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Re: [Alsa-devel] copy pcm plugin

[Jaroslav Kysela]

On Wed, 28 Jan 2004, 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.
> 
> Any thoughts? Maybe i just misunderstood the pcm copy docs though..

Yes, copy is a simple optimized variation of the route plugin, but you 
need to merge stereo devices with "multi" plugin to the multichannel 
device at first.

						Jaroslav

-----
Jaroslav Kysela <perex@suse.cz>
Linux Kernel Sound Maintainer
ALSA Project, SuSE Labs


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