[alsa-devel] explicit commandline control of speakers vs headphone output

David Henningsson david.henningsson at canonical.com
Fri Aug 27 21:26:37 CEST 2010

2010-08-27 20:46, Eric Holstege skrev:
> Thanks, Clemens;
> How were you able to determine that from the "amixer scontents" output.
> Although I can't disable *automatic* speaker mute on headphone 
> insertion, can I explicitly unmute them again (e.g. with amixer sset or 
> cset)?
> If not....
> "cat /proc/asound/card*/codec*" says it is the Realtek ALC888.
> Does this mean I have to somehow patch the kernel sound module file
> .../linux-source-2.6.*/sound/pci/hda/patch_realtek.c
> to fix this somehow?

So in the long run, I think it would be better to leave all auto-muting
to userspace. Then stuff like pulseaudio could to advanced decision of
how to handle input events. But that's the long way.

There are certainly ways to disable auto-muting for Realtek ALC888, look
along the lines of "speaker_automute" and "unsol_event". It is also
possible that you could tweak your user_pin_config to trick your HP out
into a Line Out. That way it won't automute, and you don't have to
recompile your kernel.

As a side note: The VIA HDA driver, I believe, have an option for
turning automute off. But it also sets "mute" on a misnamed control at
the same time, tricking PA into believing that you want to mute all
output. So PA is "helpful" and mutes everything else as well. :-/

David Henningsson, Canonical Ltd.

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