[alsa-devel] Mixer volume/decibel mapping
superquad.vortex2 at gmail.com
Wed Jun 9 08:19:40 CEST 2010
2010/5/21 James Courtier-Dutton <james.dutton at gmail.com>
> On 21 May 2010 07:35, Clemens Ladisch <clemens at ladisch.de> wrote:
> > James Courtier-Dutton wrote:
> >> For the cards that do have this 32bit linear value, a simple lookup
> >> table is used in the kernel code to convert it to 256 step values.
> > Which driver is this? It should be changed to use the full range.
> All creative and emu cards with a DSP.
> They use a lookup table in the driver.
seem a bug in the lookup table of alsa-lib
20log10(1/100) = -40dB , it should return -40dB if set -40dB
snd_mixer_selem_set_playback_dB(<master element>, 0, -4000, +1) -> returns 0
snd_mixer_selem_get_playback_dB(<master element>, 0, &value) -> returns 0,
sets value to -9999999
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