[linux-audio-dev] alsa mixing

Patrick Shirkey pshirkey at boosthardware.com
Wed Jan 10 01:19:26 UTC 2007

Milan Mimica wrote:
> Hello!
> We're designing a new sound subsystem for allegro game programming 
> library, and we would like to take advantages of multiple hardware voice 
> capabilities.
> On linux, ALSA is the only software that possibly could expose API for 
> such a capability, is that right? It is possible to open multiple PCM 
> outputs and play sound at the same time on all of them. The problem is 
> that we miss some basic mixing features, like panning a mono sound on 
> multichannel output for example. A similar feature is implemented as 
> 'route' ALSA plug-in that can be specified in .asoundrc file, but it is 
> not flexible enough.
> So the question is, does ALSA provide such functionality? If not, which 
> library could? Is it possible that linux OS doesn't provide any API to 
> take advantage of such hardware capabilities?

Surely this is a task that is up to the app to handle?

You would have to provide a function to move the mono signal across the 
channel array accounting for volume. It would not be too difficult once 
the base code for the channel handling was in place.

Patrick Shirkey - Boost Hardware Ltd.
Http://lau.linuxaudio.org - The Linux Audio Users guide

"Anything your mind can see you can manifest physically, then it will 
become reality" - Macka B

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