[alsa-devel] Mixer volume/decibel mapping
superquad.vortex2 at gmail.com
Wed May 26 01:00:22 CEST 2010
2010/5/25 Clemens Ladisch <clemens at ladisch.de>
> Raymond Yau wrote:
> > I have doubt about DECLARE_TLV_DB_LINEAR(ak4396_db_scale,
> TLV_DB_GAIN_MUTE, 0);
> > since the datasheet mention that dB range is only -48dB to 0dB
> > ATT = 20 log10 (ATT_DATA / 255) [dB]
> > How can AK4396 has scale of -inf DB to 0dB in the driver code ?
> When ATT_DATA = 0, there is no output, which is an attenuation of -inf.
> The next value, ATT_DATA = 1, results in ATT = -48 dB.
But snd_mixer_selem_get_playback_dB_range() does not return 48dB
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