[pulseaudio-tickets] [Bug 58313] Pulseaudio glitches volume of non-alsa applications when all alsa applications quits

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=58313

Tanu Kaskinen <tanuk at iki.fi> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |WONTFIX

--- Comment #4 from Tanu Kaskinen <tanuk at iki.fi> ---
The flat volume feature causes Pulseaudio to apply hardware volume also to
stream volumes when possible. This requires that software volume and hardware
volume changes happen synchronously. There's no reliable way to achieve that,
but Pulseaudio tries its best. It varies across hardware how well it works (it
works quite well for me).

If you don't mind disabling the flat volumes, then that's the easiest solution
to your problem. If you want to use flat volumes, there is a way to tune the
timing of the volume changes.

In daemon.conf, you can set options "deferred-volume-safety-margin-usec"
(default: 8000) and "deferred-volume-extra-delay-usec" (default: 0), which
affect the timing of the hardware volume changes. The target is to never have a
situation where the hardware volume goes up before the software volume changes
or where the hardware volume goes down after the software volume changes,
because in these cases there will be an annoying volume spike. Having error to
the other direction (having a period where the volume is too low) is not so
annoying, but it's still an error, so it's a secondary target to minimize the
delay between the hardware and software volume changes.

The delay between the two different volume changes varies to some extent, and
this variance is compensated with the safety margin parameter. If you get
volume spikes both when starting and stopping "pacat /dev/zero", then you need
to increase the safety margin.

If you get volume spikes only when starting pacat, then the hardware volume
changes are happening too early, which you can fix by decreasing the extra
delay parameter. If you get volume spikes only when stopping pacat, then the
hardware volume changes are happening too late, which you can fix by increasing
the extra delay parameter.

I'm resolving this bug as wontfix, since there's no way to automatically make
the synchronization perfect with all hardware.

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