[pulseaudio-discuss] Input sound random detection.

[Tanu Kaskinen]

On Thu, 2016-08-11 at 12:13 -0300, Gustavo Duarte wrote:
> On 8/11/16 11:23 AM, Tanu Kaskinen wrote:
> > > > Comparing the system state before and after Skype could show something.
> > You did a similar test already in the beginning, and that didn't show
> > anything else than that there were differences in volume, but nothing
> > was muted, so I don't really expect anything interesting to show up,
> > but since this is a bit more controlled test than in the beginning,
> > it's worth a shot. Here are the steps:
> > 
> > 1) Boot
> > 2) Open gnome sound settings, verify that the sound meter shows
> > activity.
> > 3) Close gnome sound settings.
> > 4) Run "amixer -c0 > before_skype.amixer".
> > 5) Run "pactl list > before_skype.pactl".
> > 6) Open Skype, call Echo / Sound Test Service.
> > 7) Try record a msg.
> > 8) No msg was hear.
> > 9) Run "amixer -c0 > after_skype.amixer".
> > 10) Run "pactl list > after_skype.pactl".
> > 11) Open gnome sound settings, verify that the sound meter doesn't show
> > activity.
> Attached you can find the outputs files.

There's nothing wrong with the mixer. However, there's another change
that Skype makes that I ignored earlier: it changes the sample rate of
the sink and source from 44100 Hz to 48000 Hz. If the hardware doesn't
work in 48000 Hz mode, that could perhaps explain why it starts to work
when you change the volume in the gnome sound settings, but not when
you change the volume with pactl (you tried that earlier, if I remember
correctly). When you change the volume in gnome volume settings, it
plays a small "blip" noise, and that changes the sink sample rate back
to 44100 Hz. The source sample rate isn't affected, so it stays at
48000 Hz, but it doesn't seem impossible that the playback sample rate
affects the capture side too in some way in the hardware.

What if you run "paplay /usr/share/sounds/freedesktop/stereo/bell.oga"
instead of changing the volume in gnome sound settings - does that make
the mic work? The paplay command should change the sink sample rate to
44100 Hz, because the audio file uses that rate.

-- 
Tanu