get two mono channel from stereo line

get two mono channel from stereo line

[arif setiawan]

Hi,

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.

Thank you for your help

Arif

Re: get two mono channel from stereo line

[Clemens Ladisch]

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

Re: get two mono channel from stereo line

[Clemens Ladisch]

arif setiawan wrote:
> It worked now. thank you. Apparently we changed something in your
> plugin sample.

Sorry, that was my error; I wrote a wrong number for the right dshare
plugin.

> The ipc_key for dshare in both left and right is supposed to be same
> right?, also for dsnoop.

Yes; the two processes that are to share the device use this to
communicate with each other.


Best regards,
Clemens

get two mono channel from stereo line

[arif setiawan]

Hi,

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.

Thank you for your help

Arif

get two mono channel from stereo line

[arif setiawan]

Thank you.
It works as we expected, however we found that we can't run two lines
(left-capture - left-playback) and (right-capture - right-playback)
simulatenously.

The error message is :
ALSA lib pcm_dshare.c:706:(snd_pcm_dshare_open) unable to open slave
cannot open output audio device right: Device or resource busy

Is there any workaround for this?