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

[Thomas Daede]

OK, here's a couple of counterexamples, still using default apps:

- I start chatting on Firefox with WebRTC and I can't hear the person
talking over my music. So I open the GNOME control center and make
Firefox louder. Pulseaudio is awesome. But now, the volume of all of my
other applications is permanently lowered, and can no longer reach max
volume. When I unplug my headphones and want to crank up my laptop
speakers, I discover my music plays back too quietly. In fact, it turns
out that now I have to open the settings and adjust every application
back up to 100%, whenever I open a new application.

- Rhythmbox's volume slider goes from 0-100%, and this changes system
master volume. I don't know of any other OS that does this - it's
certainly not the skeumorphic thing to do.

- Many web pages include a volume control, e.g. Youtube. This is always
expected to behave in the traditional (multiplicative) way, so Firefox
had to implement a soft volume control before hitting pulseaudio:
https://bugzilla.mozilla.org/show_bug.cgi?id=1046814

With flat volumes, applications initially start at 100%, and you can
change the volume up or down. Without, you can only adjust them down.
While being able to adjust both ways might be nice at first, it quickly
becomes a mess when your application's volumes end up all over the place
with some use of this feature.

To me, flat volumes seems to be a result of discovering that HD Audio's
spec provides well defined amplitude levels for the master mixer
control, and then trying to find a problem to solve with that new
ability. I don't think this one worked out.

On 09/21/2015 03:00 PM, Owen Taylor wrote:
> 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
> 
>  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
>