[pulseaudio-discuss] Splitting a sound card

[Tanu Kaskinen]

On Wed, Aug 29, 2007 at 08:25:17PM +0200, Jan Kasprzak wrote:
> 	I know of the possibility of using ALSA + dmix to 
> create virtual sound cards, but doesn't this sort of defeats
> the purpose of having PluseAudio at all?

Not in my opinion. All audio would still be flowing through
Pulse.

But this solution won't work if you can't get all the four
channels utilized in Pulse.

>From you other mail:

On Thu, Aug 30, 2007 at 01:54:17PM +0200, Jan Kasprzak wrote:
>       I have tried to use "hw:0,0" or "hw:0,1" as a module-alsa-sink
> argument, but it does not work:
> 
> W: alsa-util.c: Unable to attach to mixer hw:0,0: No such file or directory
> W: alsa-util.c: Unable to attach to mixer hw:0,1: No such file or directory

Those are just warnings, it probably prints errors too
before quitting. (It does quit during startup, right?)

> $ cat /proc/asound/pcm
> 00-01: VIA 8237 : VIA 8237 : playback 1 : capture 1
> 00-00: VIA 8237 : VIA 8237 : playback 4 : capture 1

Hmm... I have to confess that I don't really know how this
should be interpreted. For a comparsion I'll paste my setup:

00-02: ICE1724 Surrounds : ICE1724 Surround PCM : playback 3
00-01: IEC1724 IEC958 : IEC1724 IEC958 : playback 1 : capture 1
00-00: ICE1724 : ICE1724 : playback 1 : capture 1

My card has 7.1 channels, plus digital i/o. Based on that
I'm guessing my hw:0,0 is a stereo device (it has one
"stereo playback" and one "stereo capture". hw:0,1 is the
digital part of the sound card. hw:0,2, the surround part,
probably has three "stereo playbacks".

If the same logic is applied to your output, hw:0,0 has
eight channels out and two in. One can just guess, what
hw:0,1 is in your case. Digital i/o? Modem? Is the sound
card a separate card or on the motherboard? But you said
it's a 4-channel sound card. Therefore the four playbacks on
hw:0,0 are probably mono. Well, that doesn't help us much.
However, so much is now known (or rather guessed), that all
needed channels should be on hw:0,0, and thus one loading of
module-alsa-sink should suffice.

I made now a test with my own equipment. As said earlier, I
have 8 channels out. Jack starts (I couldn't test with
module-alsa-sink, because it doesn't support my card at all)
if I tell it to use 8, 6, 4 or 2 channels. With any other
number alsa refuses to cooperate. So, the fact that your
card doesn't run with 4 channels, doesn't mean that it can't
run with some other, higher number. I'd try all numbers from
1 to 8.

-- 
Tanu