[pulseaudio-discuss] Configuring alsa mixers in the "off" profile.

[Mark Brown]

On Mon, Oct 03, 2011 at 09:13:29PM +0200, David Henningsson wrote:
> On 10/03/2011 06:12 PM, Tanu Kaskinen wrote:

> >I have some hardware that needs some mixer configuration when selecting
> >the "off" profile for the alsa card in order to save power. Now that I
> >think about it, I'm not sure why the driver can't turn off the power
> >when nobody's using the device... I'll have to ask from the driver
> >developer.

If it's an embedded device this will happen automatically - when the 

> >Anyway, if we assume that there's a valid reason for keeping the device
> >powered whenever the mixer element isn't in the "Off" position, how
> >should we handle this in Pulseaudio? My suggestion is to add an "off
> >path" to profile sets. That is, the profile set configuration file would
> >have an option in the [General] section called "off-path", which would
> >have a path name as its value. Whenever the "off" profile is activated,
> >the "off path" is activated too.

> Just as an alternative, without having thought through which one is
> better, what if this is deduced by the paths?

> E g, when switching from path A to path B, that would mute
> everything not specified in path B. Switching to the "Off" profile
> would then implicitly mute everything. Would that be reasonable?

> As a side note, you seem to do more of the embedded side of things.
> What is your take on UCM and would using that solve / pose a third
> solution to this problem in this case?

UCM can implement either (or both) of the above strategies - when you
move out of a use case or disable a device it will write whatever
control settings it's told to.  But to be honest the above report sounds
more like either the driver is buggy or something is mistakenly
activating a bypass path (in which case there's probably unwanted audio
going through the system too).