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

[Raymond Yau]

> >
> > > >> 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?

Some realtek codec e.g. alc262

Supports MONO line output with independent volume control

http://www.realtek.com.tw/products/productsView.aspx?Langid=1&PFid=27&Level=5&Conn=4&ProdID=40

Badness table cannot be applied to all realtek codecs