Disable PulseAudio flat volumes to prevent it from pushing volume level to max

[Vít Ondruch]

Dne 22.9.2015 v 00:00 Owen Taylor napsal(a):
> On Thu, 2015-09-17 at 23:26 +0200, Germano Massullo wrote:
>> Il 17/09/2015 21:13, Andrew Lutomirski ha scritto:
>>> To clarify: did you get blasted by music or by video conference
>>> sounds?  If the music volume got louder, then it sounds like either
>>> a
>>> straight-up bug in PulseAudio (and a severe and dangerous one at
>>> that)
>>> or a serious bug in your video conference volume in which it
>>> adjusts
>>> the volume of streams other than its own.
>>>
>>> If you got blasted by video conference sounds, then I'd say it's a
>>> serious design flaw in PulseAudio.  PulseAudio should offer an
>>> easy-to-configure maximum volume (probably A-weighted power, but
>>> peak
>>> level works, too, if considerably less well) on a per-output basis
>>> with which to protect your ears.
>>>
>>> --Andy
>> I got blasted from the music because I was not making a conference, I
>> only logged into the software, so the music was the only sound I was
>> listening to. PulseAudio pushed the master audio level to 100%
>> (therefore all applications audio level changed to 100%, due flat-
>> volume setting).
> I'm not an expert in the subject, but I'm pretty sure this is not how
> flat volumes are supposed to work - it doesn't sound like useful
> behavior at all!
>
> Experimenting with GNOME, the model presented to the user seems to be:
>
>  - Each application's volume control separate goes from 0-100% of the
>    maximum system volume. 
>  - Adjusting each application is independent
>  - Modifying the system global volume slider proportionally adjusts the
>    volume of each application
>  - The system global volume slider is always maintained to be at least
>    as much as the maximum of any application

If this is true, than it is totally unexpected. I would expect that
system volume proportionally limits all volumes, e.g. if my system
volume is at 50%, the apps 0-100% is actually just 0-50% of system volume.


Vít

>
>  NOTE: The system global volume slider is *not the same as the hardware
>        volume and does not represent a multiplication factor for
>        application volumes. It's just something that the user can
>        drag to change the volume of all applications.
>
> There is danger to the ears if an application assumes that 100% volume
> is a safe volume and blindly sets its volume to 100% without user
> input. But that only affects that application - one application's
> misbehavior never affects another application.
>
> It sounds like KDE ends up implementing a different model, either
> intentionally or because of bugs. It's also possible that lower level
> bugs (sound card driver, for example) might be making things misbehave.
>
> In general, the fact that pulseaudio is configurable in this area is
> going to be the source of almost infinite bug chasing, as applications
> and desktop environments are "fixed" for one setting or another. It's
> also very easy for people to stop investigating problems and say that
> "changing the setting fixed it for me." :-(
>
> - Owen
>