Re: Surround sound and volume control question

[Daniel Jacobowitz <drow@false.org>]

On Mon, Oct 09, 2006 at 03:37:49PM +0200, Takashi Iwai wrote:
> At Sun, 8 Oct 2006 18:27:26 -0400,
> Daniel Jacobowitz wrote:
> > 
> > How is volume control supposed to work for surround sound codecs?  Is there
> > typically a register which affects every channel, or do you have to adjust
> > them separately?  I've been staring at the datasheets and prodding the
> > registers for mine (ICE1724, on a Shuttle SN25P).  There's three pieces:
> > the vt1720, the vt1617a, and a wm8728.  The vt1617a has ac97 volume control
> > registers, but the "master" volume doesn't affect the center/lfe or rear
> > surround channels.  I am guessing that the wm8728 is just for the last two
> > channels (I've got jacks for 7.1 but the vt1617a only does 5.1).
> 
> That's the standard behavior of AC97 codec.  The "master" doesn't
> influence on surrounds.  Some ac97 codec chips have an extended mode
> that behaves differently, though.

I assume this one doesn't.  But could you tell me one supported card
which does, so that I can compare?  Thanks.

> alsactl save & restore should work for softvol.
> The softvol mixer element doesn't exist only at the very fresh state.

I see, I just tried it and alsactl will create a user control just
fine.  That's great.

I will give the softvol solution a try, and post the patches if it
works.

-- 
Daniel Jacobowitz
CodeSourcery

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