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. > BTW , if ymf7xx (DSP) only accept 16 bit digital PCM data and output to > 18-20 bit AC97 codec , The DSP uses more precise values internally. > how can the per stream volume control has a scale -inf dB to 0dB ? multiplication factor 0: dB = 20 log10(0) = -inf multiplication factor 1: dB = 20 log10(1) = 0 This is true regardless of the precision of the multiplier. Even a one- bit factor behaves like this; in fact, this would describe a mute switch. HTH Clemens _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
