[linux-audio-user] Re: [Alsa-devel] dmix vs alsaplayer [was jackd, zynaddsubfx and iiwusynth]

Kai Vehmanen kai.vehmanen at wakkanet.fi
Mon Mar 3 14:19:00 EST 2003

On Tue, 4 Mar 2003, Patrick Shirkey wrote:

>> Has anyone tried the dmix plugin thats part of alsa rc8?  This looks 
> I was fscking around with it on Saturday. So far I have managed to use 
> multiple instances of aplay but other apps like alsaplayer bork at it. I 
> have yet to figure out why but I think I should probably submit a bug 
> report somewhere.

I've tried it with ecasound and seems to work just fine. One catch is that 
dmix only supports a certain set of audio format parameters at a time. You 
can change these via asoundrc (or dmix:x,y), but not at run time. Anyway, 
with default dmix installation (on top of snd-intel8x0 hw):

ecasound -i foo.wav -o alsa,dmix -b:4096 &
ecasound -i bar.wav -o alsa,dmix -b:4096

... plays the two files at the same time. -b:4096 is needed because of the 
abovementioned reasons.

> $ alsaplayer -o alsa -d plug:\'dmix:SLAVE=\"hw:2,1\",RATE=44100\' 
> track_8.wav
> error on set_period_size (1024)
> Unavailable hw params:

Try matching the alsaplayer period_size to the one used by dmix with 
the "-f 22052" alsaplayer option. 

PS Opening dmix in non-interleaved mode produces totally garbled output:
   "ecasound -i foo.wav -f:16,2,44100,n -o alsa,dmix -b:4096"

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