[LAD] Is there a Linux Software Mixer?

Rory Filer rflyer at gmail.com
Wed Dec 1 03:21:22 UTC 2010

> On Tue, Nov 30, 2010 at 5:52 AM, Paul Davis <paul at linuxaudiosystems.com> wrote:

> There are two approaches to the situation of multiple applications
> using one soundcard.
> One involves using the capabilities built into ALSA itself. This means
> making each application open a dmix device.

Bingo! I've been playing with this and got it working using "aplay" on
my embedded platform. I can play two tracks simultaneously now and
hear them both. In order to get it working I had to resolve a configuration
problem by adding "/etc/asound.conf" and I copied one from a posting:

pcm.playback {
type dmix
ipc_key 2048
ipc_key_add_uid true
ipc_gid 1
slave {
rate 44100
pcm hw:0

The "ipc_gid" parameter was giving me trouble until I did this. My aplay
command works when I use "-D playback" on both commands. Simple
for you guys maybe, but quite a thrill for me :)

I tried to run my squeezeslave client this way too, but it wants to go
straight and hog the /dev/dsp interface. So when I try running my aplay
while squeezeslave is up I get

"audio open error: Device or resource busy".

And Squeezeslave only supports numbers when specifying output devices.
Run it with the -L option and you see

Output Devices:
* 0: /dev/dsp

I'm inclined to try and alter squeezeslave to accept an argument like
aplay's -D. Failing that, ...

> The other involves using a user-space server.
... I might give this a try

Thanks for the help!


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