[pulseaudio-tickets] [Bug 39700] Acer Aspire One: microphone only works after turning left microphone channel off

bugzilla-daemon at freedesktop.org bugzilla-daemon at freedesktop.org
Wed Feb 8 23:54:48 PST 2012


--- Comment #4 from David Henningsson <david.henningsson at canonical.com> 2012-02-08 23:54:48 PST ---
We have a workaround (i e quirk) for some of these in the kernel already. We
write to some secret register, that turns the Internal Mic into a Mono mic. So
if you're having ALC269 or ALC271X (as seen in /proc/asound/cardX/codec#X ) you
can just submit a quirk to the kernel. 

Unfortunately I've also seen it happening for ALC268 and ALC272X (and IIRC, one
Conexant?) and we don't know the secret register for those (yet). 

There are various ways we can work around this in both the kernel, alsa-lib and
PulseAudio layers. It's a matter of picking the right one. I'm leaning towards
trying to fix it in the kernel's codec drivers, because
1) we already have quirking infrastructure there
2) we already have some working quirks already in that layer
3) it would benefit other sound applications that use ALSA directly.

The downside to that is really that we're silencing out one channel for
everyone, leading to no application being able to use both channels, even if
they would implement some kind of "auto-detect-and-reverse-one-channel"
functionality. But should such need arise later on, we could possibly implement
a kcontrol to switch this functionality on and off...

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