2010/5/25 Clemens Ladisch <clemens@xxxxxxxxxx> > Raymond Yau wrote: > > 2010/5/21 Clemens Ladisch <clemens@xxxxxxxxxx> > > > 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 > based. > > Now if you have some remark or question, you should remember to include > it in your mail. > > > Regards, > Clemens > 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 , DR and S/N is only 120dB ATT = 20 log10 (ATT_DATA / 255) [dB] How can AK4396 has scale of -inf DB to 0dB in the driver code ? BTW , if ymf7xx (DSP) only accept 16 bit digital PCM data and output to 18-20 bit AC97 codec , how can the per stream volume control has a scale -inf dB to 0dB ? inf dB may occur when DSP accept floating point however the storage of Float pointing is still finite , the min dB of DSP accept FLOAT64 should in theory lower than the min dB of those DSP accept FLOAT32 _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
