Linux kernel 3.6 audio distortion/noise

Since I’ve spent a few hours of my time tracking the source and potential workarounds for this annoying bug, I figured that I may as well document my findings here. The latest Linux kernel (i.e. 3.6.0 at the time of writing) has a bug whereby if you play any audio file in VLC and try to change the volume, you’ll hear a very annoying amount of audio distortion/noise. However, neither mplayer nor gstreamer-based players (Rhythmbox, Totem, etc.) seem to be affected (at least, not for me). More details available on the LKML, where I’ve compiled my findings. I don’t seem to be the only one affected at least (e.g. LKML#1, LKML#2, alsa-devel#1, alsa-devel#2, bugzilla).

Workarounds: (obsolete, see update below)

1) Revert commit c20c5a841cbe47f5b7812b57bd25397497e5fbc0 and re-compile your kernel.

2)

# echo "options snd-hda-intel position_fix=2" >> /etc/modprobe.d/alsa-base.conf
# alsa force-reload
$ pulseaudio -k

(Or just reboot instead of reloading ALSA modules + restarting PulseAudio.)

I’ll update this post if I find other workarounds, or if my diagnosis of this bug is completely off. In the meantime, I’m off to enjoy some distortion-free music with VLC.

Update: Fixed in 3.6.2 (and 3.7): patch can be found on the LKML.

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