[pulseaudio-discuss] Left/right volume unlinked in hardware?

[Marti Raudsepp]

Hi list,

When I adjust the volume in PulseAudio, I noticed that the volume for
my left speaker is being reduced more than the volume of my right
speaker. The difference is small, but annoying enough when using
headphones.

So I set out to investigate with alsamixer and found that PA always
prefers scaling the "Front" volume control. When I set this control to
100%, everything sounds fine, but reducing it does indeed introduce
the difference I mentioned above, even if the volumes are linked in
alsamixer.

Other volume controls such as "Master Front", "PCM" etc seem to be unaffected.

So as a workaround, I start up mplayer, pause it and set it to 100%
volume in PA, which forces software gain control.

I don't think this is an ALSA problem? ALSA just simply interfaces all
those volume controls to the user and can't help if some of them are
broken.

Since PulseAudio takes control of setting the levels, I think it's
also PA's responsibilty to also know about such hardware quirks?

I assume that I'm not the first person to find a problem with a hw
mixer control, but I couldn't find any such "quirk databases" in
PulseAudio source tree.


lspci -nn:
00:14.2 Audio device [0403]: ATI Technologies Inc SBx00 Azalia (Intel
HDA) [1002:4383]

aplay -l:
card 0: SB [HDA ATI SB], device 0: VT1708B Analog [VT1708B Analog]
  Subdevices: 1/2
  Subdevice #0: subdevice #0
  Subdevice #1: subdevice #1
card 0: SB [HDA ATI SB], device 1: VT1708B Digital [VT1708B Digital]
  Subdevices: 1/1
  Subdevice #0: subdevice #0


Regards,
Marti