[alsa-devel] 2 speakers are assigned to the same DAC, this can't support 4.0/2.1 channles

[Takashi Iwai]

At Wed, 10 Jun 2015 12:28:39 +0200,
Takashi Iwai wrote:
> 
> > >> A cleaner way would be to prepare a different badness table for the
> > >> speaker, and increase the value for shared_surr.  An untested patch is
> > >> below.
> > > Got it, I will test it soon. Thanks.
> > >
> > Hi Takashi,
> > 
> > Your patch can fix the problem, it works very well.
> 
> OK, good to know.  I'd like to test a bit more via hda-emu whether
> this gives any ill effects.  So far, this seems fixing a few other
> machines, too, so it's a good thing to have in general.

This change alone results in regressions on machines that are capable
of 4.0/5.1 surrounds.  For avoiding it, the badness for multi-io has
to be increased as well.  It's damn sensitive.

But, now I wonder now whether blindly applying this is good.  Suppose
a machine with 2.1 speaker and one headphone, but the codec has only
two DACs.  With this setup, now the headphone and the speaker share
the same DAC, as the cost of having individual 2.1 speaker volume.
Is this more useful than having individual volumes for speaker and
headphone?

Maybe the machine you're trying to support has a different situation.
So applying the new rule to limited devices is fine.  But if so, it's
not necessarily to be an adjustment of badness table, but just you can
provide the simple DAC/pin preference map explicitly in the fixup.


Takashi