[alsa-devel] Mixer volume/decibel mapping
clemens at ladisch.de
Tue May 25 10:45:50 CEST 2010
Raymond Yau wrote:
> 2010/5/21 Clemens Ladisch <clemens at ladisch.de>
> > DB_LINEAR means that the mixer control value is a multiplier for the
> > PCM sample value, as James wrote. A DB_LINEAR mapping has
> > 0 == -infinity dB, full scale == 0 dB, and the mapping between mixer
> > control values and corresponding dB values it _not_ linear.
> pci/oxygen/oxygen.c:static const DECLARE_TLV_DB_LINEAR(ak4396_db_scale, TLV_DB_GAIN_MUTE, 0);
> pci/oxygen/hifier.c:static const DECLARE_TLV_DB_LINEAR(ak4396_db_scale, TLV_DB_GAIN_MUTE, 0);
> Refer to AK4396 datasheet
> Output Volume
> The AK4396 includes channel independent digital output volumes (ATT) with
> 256 levels at linear step including MUTE.
> These volumes are in front of the DAC and can attenuate the input data from
> 0dB to –48dB and mute.
> dB range is -48dB to 0dB only
> ATT7-0: Attenuation Level
> ATT = 20 log10 (ATT_DATA / 255) [dB]
> FFH : 0dB (Default)
> 00H : Mute
This is the section of the datasheet on which the above declarations are
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