[alsa-devel] Verifying mixer dB data/Invalid dB data from USB cards, especially Aureon 5.1 MkII

[Mark Brown]

On Wed, Feb 17, 2010 at 12:56:58AM +0100, Lennart Poettering wrote:

> Nah. I actually don't need this value for PulseAudio. In PulseAudio I
> chose to shift all scales so that maximum amplification becomes 0 dB,
> so that the UIs are similar to how most hifi racks do it, and which I

Interesting.  The hifi equipment I've dealt with typically doesn't
present any units at all in the UI outside of level monitors.

> think is a nice, easy and understandable logic. That way my volume
> scales range from -inf dB to 0 dB in all cases, regardless of the
> hardware/drivers in use. Of course, that means that ALSA's own 0dB is
> not directly visible on the scale. Because it might be sometimes
> useful to know where it is, we export that position as "base volume"
> and the UIs show it with a little marker at the side.

Yeah, the actual zero point is definitely needed - it gives an
indication of the expected output level which is very useful during
setup.

I really do need to find time to dig into this code at some point -
there's also the digital vs. analogue gain thing I've mentioned to you
before that I wanted to look at.