Re: Sound detection

[Liam Girdwood <lg@opensource.wolfsonmicro.com>]

On Thu, 2007-01-25 at 17:09 +0100, Takashi Iwai wrote:
> At Thu, 25 Jan 2007 16:03:29 +0000,
> Liam Girdwood wrote:
> > 
> > On Thu, 2007-01-25 at 13:36 +0100, Takashi Iwai wrote:
> > > At Sun, 21 Jan 2007 13:39:35 +0100,
> > > Andreas Corneliussen wrote:
> > > > 
> > > > Hi
> > > > I've just build a mediacenter, and is about to construct an hifi 
> > > > amplifier for it. Therefore i would like to know a way to make alsa 
> > > > detect when nothing is playing at the output, and then run a external 
> > > > command. And detect when something has started playing at the output, 
> > > > and run an external command before any output is generatet.
> > > > This I would like to do, because I then could make an interface between 
> > > > the amplifier and the computer to make sure that it does not use anymore 
> > > > standbypower than needed.
> > > 
> > > It's an interesting question.  Currently, there is no good framework
> > > for such a functionality, so you need to build something new.
> > > 
> > 
> > Fwiw, the Dynamic Audio Power Management code in ASoC (Alsa for SoC
> > devices) does this very thing. Please feel free to have a look and take
> > code if required.
> 
> But it doesn't communicate with the user-space, right?

Your right, it only powers on board components and can't communicate
with user-space atm.

> I supposed that the power-management stuff isn't built in the driver
> itself...
> 

The codec and machine power maps are in the driver, but it's controlled
via the ASoC core (and ultimately via alsa-lib)

Liam



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