Re: Major problem with the current alsa mixer.

[Takashi Iwai <tiwai@suse.de>]

At Fri, 12 Sep 2003 09:23:13 +0200 (CEST),
Jaroslav wrote:
> 
> On Fri, 12 Sep 2003, James Courtier-Dutton wrote:
> 
> > There is a MAJOR problem with the current alsa mixer.
> > How do I set a mixer volume to the 0 db point. I.E. no attenuation, and
> > no gain.
> > Currently, we might have a value from 0 to 100%. Percent of what?
> 
> Percent of the volume range.
> 
> > What this value means varies depending on the sound card hardware being
> > used.
> > I think that this should all be changed to signed values, with a max and
> > a min setting. With a value of 0 being equivalent to no-gain,
> > no-attenuation. Each alsa-driver would then convert this signed value
> > into a value actually written to the hardware register via a lookup table.
> 
> Things are not as easy as you like. Using the signed notation for the
> volume representation does not sound bad, but on the other side, it's
> great to have zero as minimum value as well.
> 
> I have plans to extend the mixer interface to pass (and handle) the dB
> resolution. But it will be done completely in the user space. The alsa-lib
> will analyze information from the driver (hardware components) and then it
> will use a predefined expressions for these transformations. I think that
> we should not polute the kernel space with these "additional" things.

agreed.  it's a user-space thing.

but some additional information like min/max dB would be needed, too?


Takashi


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