[pulseaudio-discuss] Controlling pulseaudio volume with kmix

[Piero Filippin]

Lennart Poettering wrote:
> On Sat, 30.05.09 12:03, Piero Filippin (filippinp at yahoo.co.uk) wrote:
>
>   
>> Hi,
>> first of all I want to thank everyone for their work on pulseaudio. I  
>> always thought Linux audio sucked, finally something which make sense  
>> (and works)!
>> I enabled the a52 in asound.conf, and finally I can enjoy surround sound!
>>
>> However, I am having 2 issues. First of all, for some reasons I cannot  
>> understand, I cannot use the a52 output on pavucontrol, the sound is  
>> "choppy", this means something like 100ms of audio every second - but  
>> "simultaneous output on a52" works like a charm. Just a weirdness.
>>     
>
> This is probably an issue with the timing logic in the a52 ALSA
> backend. pavucontrol sets rather short latency settings on all devices
> to be able to show the PCM monitoring meters that closely reflect what
> you actually hear. These lower latency settings probably break the a52
> backend.
>
>   
What I found weird is if I pick "simultaneous output on a52" it works 
smooth. In my understanding the "simultaneous" is supposed to 
"broadcast" the audio to all the cards. As I have only one card, this 
should not make absolutely no difference (but probably the timings are 
more relaxed, fixing the problem).

> Please note that Fedora does not ship that module due to patent
> issues, and hence I have never tested if it actually works. I wrote
> the a52 logic in PA without ever having tested it.
>
> It would probably be a good idea to include the a52 logic directly in
> the PA plugin to fix all the timing issues, instead of relying on ALSA
> for that. But uh, given the broken patent situation this is unlikely
> to happen anytime soon. Sorry.
>
>   

>> The only serious issue: I am not able to do is to change the volume with  
>> kde4 kmix (I was able to before enabling a52). I can change the volume  
>> on every single application (eg volume slider in amarok2 or mplayer) or  
>> using pavucontrol, but changing the volume in kmix has no effect (only  
>> the master mute works, and it was not working before).
>>     
>
> On KDE ymmv. Try using the newest g-v-c. Please note that legacy
> mixers like kmix tend to expose the full low-level analog alsa mixer. If you
> use digital output that is useless, use the PA volumer control
> instead, either in the form of pavucontrol or at a lower level with
> pacmd/pactl.
>
> Lennart
>
>   
Thank you a lot - this is what was trying to find out - kmix not 
controlling pulse is not a problem with my configuration.
This is definitely kmix fault, it refuses to work with anything else 
than hw:X. Pulse works fine with alsamixer (even is in my configuration 
the channels are in the wrong order, but this is an alsa issue).

To solve my problem (pavucontrol is not usable if you are watching a 
movie) I mapped the multimedia keys in my keyboard to "amixer set Master 
10%-" and "amixer set Master 10%+" (channels' volumes are linked together).

I had no luck with pacmd/pactl (last time I tried there was no support 
for volume increment/decrement, just absolute).



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