Independent usage of two channels

Independent usage of two channels

[Pavel Fedin]

 Hello!

 I'm novice in ALSA programming and i've got a question.
 Is it possible to use two channels of a sound card as two independent
devices for PCM playback? I'm making a PC-based security system, and i
would like to use one channel as a voice feedback for control panel
and another one - as a software-driven siren.

 Kind regards

Re: Independent usage of two channels

[Clemens Ladisch]

Pavel Fedin wrote:
> Is it possible to use two channels of a sound card as two independent
> devices for PCM playback?

The sound card is probably not able to handle two independent mono
streams, but it is possible to use alsa-lib's software plugins to
emulate two devices on top of the real one.

Put this into your ~/.asoundrc or into /etc/asound.conf:

pcm_slave.stereo_slave {
	pcm "hw:0"          # or "hw:1" for the second card ...
	channels 2
}

pcm.left {
	type plug
	slave.pcm {
		type dshare
		slave stereo_slave
	}
	bindings [ 0 ]
}

pcm.right {
	type plug
	slave.pcm { type dshare slave stereo_slave }
	bindings [ 1 ]
}

Then use device names "left" and "right" instead of "default".


HTH
Clemens