[alsa-devel] Master vs. Front/Rear/LFE/... elements

Mark Brown broonie at sirena.org.uk
Tue May 12 11:21:05 CEST 2009

On Tue, May 12, 2009 at 08:47:31AM +0100, James Courtier-Dutton wrote:

> Once we have the global definition, we can then fix each driver to
> comply with it. In some cases we will have to add virtual controls.


> I personally think that the user should set the global speaker
> settings, the master, front, rear etc. controls and then just leave
> them.
> I think applications should only control their own PCM channel volume,
> and not touch the master volume at all. PA could then further control
> PCM channel volumes, by for example automatically attenuating the
> sound of an application when it gets put in the backround, if the user

This is starting to sound a lot like the stuff that's been talked about
for the scenario API in an embedded context - it has a similar idea of
having a central application managing the overall setup of the card and
giving applications something simpler to work with:


We don't want to force the use of per-application volume since that will
be too expensive for some systems, but a system that arranges for there
to be a standard control that the application should use for things like
master volume can support either a per-application control or using the
hardware control directly.

It's not always going to be possible to provide a fixed setup in the
driver since in systems like smartphones the arrangement of controls can
change very substantially depending on software controlled 

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