[linux-audio-user] ALSA: What is the website missing?

Mark Knecht markknecht at comcast.net
Mon Dec 1 20:38:30 EST 2003

On Mon, 2003-12-01 at 16:42, Benjamin Flaming wrote:
> Here's another vote in favor of this.  I suspect that .asoundrc is probably 
> ALSA's most powerful and underused feature - simply due to lack of accessible 
> documentation.  Suggested TOC:
> - What is .asoundrc
> - What you can do with .asoundrc
> - What you *cannot* do with .asoundrc
> - Basic syntax
> - Examples
> |)
> |)enji

Yes! Please!

For instance, I'll bring up an example that I hoped would work, but for
me it didn't. It sure would be nice if it did. When I use any OSS
application, then all 26 software inputs on my HDSP 9652 get the stereo
signal instead of just 2. This causes the signal to potentially get
routed to many places based on how my hardware mixer is set up.

It's most likely not working because I've made a mistake, but if this
thread could turn into an answer for me, and then other examples of how
to do things

To get around this problem, Kai provided an example of how I might tell
Alsa to only use two playback channels. My .asoundrc file today is:

pcm.hdsp {
           type hw
           card 0

ctl.hdsp {
           type hw
           card 0

pcm_slave.hdsp {
          pcm "hw:0"
          channels 26

pcm.playback_5_6 {
          type dshare
          slave hdsp
          ipc_key 314159265    # some unique number
          ipc_key_add_uid yes  # "no" to let multiple users share it
          bindings {
                0 5
                1 6

pcm.dsp0 {
          type plug
          slave pcm.playback_5_6

The hope here was that somehow OSS would find pcm.dsp0(I guess  and then
only use playback channels 5 & 6. It doesn't work. OS apps still find
all 26 channels and cause me problems unless I adjust my routing.

Anyway, maybe someone will see what I don't see and explain it to me so
it will work. (If it can work.)


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