[pulseaudio-discuss] Muting while changing ports

[Tanu Kaskinen]

On Thu, 2011-09-22 at 10:00 +0300, David Henningsson wrote:
> On 09/21/2011 04:16 PM, Tanu Kaskinen wrote:
> > On Wed, 2011-09-21 at 17:08 +0300, David Henningsson wrote:
> >> On 09/21/2011 02:22 PM, Tanu Kaskinen wrote:
> >>> Hi,
> >>>
> >>> There exists audio hardware that produces annoying noise (snap, crackle,
> >>> pop) when changing the alsa mixer settings, unless hw mute is used
> >>> during the mixer changes. I'm planning to fix this by using hw mute
> >>> during path activation, if the path provides hw mute. If anyone has
> >>> objections or other comments, the best time to publish them would be
> >>> now :)
> >>
> >> Does not sound like anything I would like to enable by default - e g,
> >> what if hw mute introduces a click, and changing the volume does not?
> >
> > If you think that such hardware is likely to exist,
> 
> It seems more likely than what you're describing, but take that with a 
> grain of salt - I have no real data to back it up.
> 
> > then I guess I'll
> > have to make this configurable, and disable it by default. The path
> > configuration files would get a new option for the [General] section:
> > "mute-during-activation = yes/no". Does that sound ok to you?
> 
> May I ask if this is driven by specific (non-PC) hw where you experience 
> this problem, or if you see a general need for it?

Yes, this is driven by specific non-PC hardware.

> Anyway, it seems that the logical place to put this in would be at the 
> (udev quirkable) card level, that way PA could potentially ship with a 
> quirk database for hw that needs this enabled. Do you agree?

Do you mean that the "mute-during-activation" option should be in the
profile-set files instead of path files? Maybe... Which would be better:
make it configurable for the whole card, or at mapping level? All
mappings of one card might not suffer from the same problems... Doing it
at the path level would give even more granularity. For my case it
doesn't matter - I'll enable the muting for all paths of the problematic
card anyway.

Regarding udev-quirkability - I don't know how useful that would be in
this case. Our alsa mixer configuration files contain eg. volume tunings
that are specific for this particular device. If the same chips are used
in a different device, the same settings may not be appropriate. We
don't use module-udev-detect, so the udev configuration files don't
exist. That said, if someone wants to write such files, that can be
done, and it doesn't actually matter whether the mute option is at card
or at path level - it's possible to use custom path files in the profile
set file given in the udev rules (the default paths for PC machines are
useless anyway).

As a sidenote, I made the change (without the configurability) and it
didn't help as much as I hoped...

-- 
Tanu