21 May
2009
21 May
'09
5:48 p.m.
On Thu, May 21, 2009 at 8:27 PM, Lennart Poettering <mzynq(a)0pointer.de> wrote:
From reading through the ALSA drivers I know that a
lot of sound card
mixer controls usually have a much higher dB resolution near 0dB then
the have near -90dB. Most of the time the steps they choose are very
arbitrary however.
There is an IEC standard for this mapping in meters (IEC 60-268-18)
which works OK for faders as well if extended in a sensible way down
to -inf, particularly if you don't want to go above 0dB. It divides
the range up into several sections which are individually linear in
dB. There's code for this mapping in several places, including
base/AudioLevel.cpp in the Rosegarden source code.
A cubic mapping is also good.
Chris