[pulseaudio-discuss] Volume jumps to 100% on KDE startup in KDE 4.4.0-4.4.1

Colin Guthrie gmane at colin.guthr.ie
Mon Mar 15 15:03:50 PDT 2010

'Twas brillig, and Dwight Paige at 15/03/10 18:50 did gyre and gimble:
> On 03/14/2010 06:17 PM, Colin Guthrie wrote:
>> Pulseaudio expects full control over the mixer levels and what you are
>> seeing here is a feature called "Flat Volumes" in action. At some point
>> the volume of the logout sound has been saved to be 22% (perhaps not
>> exactly that but some value). In order to achieve that result, PA will
>> try whenever possible to use h/w volume adjustments rather than software.
>> As PA is a mixer, it will take the loudest volume of any running stream
>> and use that as the hardware volume and then attenuate in software any
>> other streams so that they are set to their relative values.
>> e.g. say I have a stream running at 50%, then the h/w will be set to 50%
>> and the stream will not be attenuated at all in software. If I then play
>> a second stream at 75%, the h/w volume will increase to that value and
>> the current running stream @50% will be attenuated in software so that
>> it stays at 50% overall.
>> So it's not exactly unusual to see the h/w volume jump around. What is
>> more interesting is why the logout sound is played more quietly... Can
>> you make sure the "System Sounds" slider in pavucontol has a sensible
>> value?
> Sound system volume is now set to 70%. I believe original setting after
> install was 0%.

Yeah this is a presentation bug... I've been meaning to fix this in
pavucontrol. I already initialise it to 100% in kmix.

>> If possible try and grab "pacmd ls" when the shutdown sound is playing
>> as it will say what "stream-restore.id" is being used for the logout
>> sound itself which may explain where the lower volume setting came from.
> I did run 'pacmd ls' while startup sound was playing. I can't interpret
> for myself contents of 'pacmd ls' so I created a pastebin of it:
> http://pastebin.ca/1841461

Sure, it's a bit complicated but here's what's up:

The logout sound itself is shown as a "sink input" (i.e. the input to a
sink) on line 484. In it's property list it has a "media.role" as
"event". This means it's volume will be subject to the value of the
"System Events" slider in pavucontrol (and in the newer kmixes).

The sink itself is show on line 227. It has a volume of 31%. If you take
your 70% System Sounds, you get the final volume of 22% which is what
your Sink Input (on line 484) reports.

Now although the "volume" of the sink is reported as bing 31% in this
output, it will likely actually set the underlying h/w to 22% as only
one stream is playing. This is flat volume logic at work. If another
stream was started at a 100% stream volume, the h/w volume would have to
jump up to 31% again.

So the question perhaps still remains as to why your main volume was set
to 31%. Is this expected?



Colin Guthrie

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