Today is a momentous day for my ears. After years of mucking about with ALSA and .asoundrc files, I can finally say I have been able to achieve simultaneous sound streams on my linux box. Admittedly, by years I mean maybe a couple of times a year, for only a few hours at a time, but at least I have finally done it. I am not talking about some cheaters way of doing it either, like piping it through aRts, ESD or any other sound server. I have actually got ALSA itself to mix sound streams on the fly using Dmix.

Previously, if I was listening to music while chatting away in Gaim, all of the Gaim sounds would queue behind the current stream. So when I stopped the media player, I would get a rush of repeating “message received” sounds as alsa emptied the queue. Sometimes this could go on for a few minutes or more - very annoying to say the least. Well, such annoyances are now a thing of the past, and my ears are rejoicing in the audio-goodness that ALSA is now pushing out.

Here is how I did it.

I simply added the following to my .asoundrc file in my $HOME directory:

pcm.dmixer {
type dmix
ipc_key 1024
slave {
pcm "hw:0,0"
period_time 0
period_size 1024
buffer_size 8192
rate 44100
}

bindings {
0 0
1 1
}
}

pcm.dsp0 {
type plug
slave.pcm "dmixer"
}

pcm.!default {
type plug
slave.pcm "dmixer"
}

pcm.default {
type plug
slave.pcm "dmixer"
}

ctl.mixer0 {
type hw
card 0
}

So simple, and only 36 lines of code.

This entry was posted on Monday, March 7th, 2005 at 6:42 pm and is filed under Linux. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.