[pulseaudio-discuss] PA volume effects

[Daniel Mack]

On Mon, Apr 27, 2009 at 06:43:08PM +0200, Lennart Poettering wrote:
> > I'm observing strange audio artefacts with my audio driver which seem to
> > be related to audio material overamplification. IOW, the effect is only
> > audible at waveform peaks. When I attenuate the playback volume
> > pavucontrol, things get a lot worse - horrible distortion all over
> > the place, even in more quite audio sections.
> > 
> > Also, when comparing the audio output of 'aplay -Dpulse foo.wav' with
> > 'aplay -Dplughw foo.wav', it is clearly audible that PA adds some kind
> > of amplification to the material (I would guess ~3dB), even though all
> > GUI accessible levels are set to 100%.
> > 
> > The driver I'm working on does not have any volume control features,
> > hence this must be done in software.
> > 
> > Has that been encountered before?
> 
> Please try to reproduce this, then do "ls" in pacmd and paste it
> somehere. This should show if PA does digital amplification for any of
> the active streams.

It's always reproducable, here is the output:

	http://caiaq.de/download/tmp/pacmd-distortion.txt

Let me know if I can provide more details.

Thanks,
Daniel