> I seek to use my onboard 4 ch sound in a two stereo setup. so I can
> connect a headset to the rear speakers.
> I am using gentoo with kernel 2.6.21-ck2-r1 and the alsa provided in the
> kernel 1.0.14rc3.
You realise this would mean one audio device would play out of the front
speakers and a different one out of the rear speakers? i.e. if you're
listening to music and you want to put the headset on, you'll need to
stop the music, change the audio device, then start the music again...
> the only way I may hear anything from the line-in/rear connector is when
> running this:
> $ aplay -D plug:surround40 sound.wav
surround40 is a four-channel device, yes.
> I tried this in my .asoundrc file:
>
> pcm_slave.via4 {
> ~ pcm "hw:0"
> ~ channels 4
> }
>
>
> pcm.ch12 {
> ~ type dshare
> ~ slave via4
> ~ ipc_key 47110815
> ~ ipc_key_add_uid no
> ~ bindings {
> ~ 0 0
> ~ 1 1
> ~ }
> }
>
> pcm.ch34 {
> ~ type dshare
> ~ slave via4
> ~ ipc_key 47110816
> ~ ipc_key_add_uid no
> ~ bindings {
> ~ 0 2
> ~ 1 3
> ~ }
> }
This is a complete guess, but does it work if you use "surround40" as
the slave device? (either in the pcm.ch34 or via4.) I'm guessing the
problem lies in that you've got two 2-channel devices, and you're trying
to mix them into a single 4-channel device - i.e. ALSA expects four
incoming channels from each stream, but you're only delivering two.
Presumably you'll need something like this:
pcm.ch34 {
...
bindings {
null 0 # Not real code, just illustrating a point
null 1
0 2
1 3
}
}
If you did something like this, you'd be outputting a 4-channel audio
stream, with two of the channels as silence. There should be no
problems dmixing that. I don't know the correct method for creating
some silence channels, but perhaps somewhere here could point that out.
Cheers,
Adam.
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