From mboxrd@z Thu Jan  1 00:00:00 1970
From: Clemens Ladisch <clemens@ladisch.de>
Subject: Re: get two mono channel from stereo line
Date: Fri, 24 Jul 2009 11:09:35 +0200
Message-ID: <4A697A4F.6000809@ladisch.de>
References: <c697747b0907232107k749c413bx2a88ccc97505447b@mail.gmail.com>
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To: arif setiawan <n.arif.setiawan@gmail.com>
Cc: alsa-devel@alsa-project.org
List-Id: alsa-devel@alsa-project.org

arif setiawan wrote:
> We have a beagleboard with one audio line-in and one audio line-out. From
> the documentation both are stereo line. Now we want to use four mono audio
> line for our system. two input from radio and microphone, two output to
> radio and speaker. We use ALSA and we would like to know how we can achieve
> this either by plugin or programming alsa.

Try something like this:

pcm_slave.stereo {
	pcm "hw:0,0"	# or whatever your device is
	channels 2
}

pcm.left {
	type asym
	playback.pcm {
		type plug
		slave.pcm {
			type dshare
			slave stereo
			ipc_key 200907241
			bindings [ 0 ]
		}
	}
	capture.pcm {
		type plug
		slave.pcm {
			type dsnoop
			slave stereo
			ipc_key 200907242
			bindings [ 0 ]
		}
	}
}

pcm.right {
	type asym
	playback.pcm {
		type plug
		slave.pcm {
			type dshare
			slave stereo
			ipc_key 20090724
			bindings [ 1 ]
		}
	}
	capture.pcm {
		type plug
		slave.pcm {
			type dsnoop
			slave stereo
			ipc_key 200907242
			bindings [ 1 ]
		}
	}
}


HTH
Clemens