On 25 May 2010 09:38, Clemens Ladisch <clemens@xxxxxxxxxx> wrote: > Raymond Yau wrote: >> 2010/5/21 Clemens Ladisch <clemens@xxxxxxxxxx> >> > Peter Ujfalusi wrote: >> > > The DB_SCALE also provides linear mapping: >> > > For example, if the HW volume control has a range 0 .. 100 >> > > In HW these means: >> > > 0 == -10dB, 1 == -9.8dB, 2 == -9.6dB .. 99 = 9.8dB, 100 = 10dB >> > > So it is linear. >> > >> > This is not what is meant by "linear", because dB values are not linear. >> > >> > DB_LINEAR means that the mixer control value is a multiplier for the >> > PCM sample value, as James wrote. A DB_LINEAR mapping has > > ... in practice ... > >> > 0 == -infinity dB, full scale == 0 dB, and the mapping between mixer >> > control values and corresponding dB values it _not_ linear. >> > >> > TLV_DB_LINEAR_ITEM is a quite misleading name, but it actually means >> > "dB mapping for a mixer control whose value has a linear effect on the >> > sound output", _not_ a linear value <-> dB mapping. >> >> seem max(full scale) is more then 0dB for some codecs , only three drivers >> have 0dB as max and TLV_DB_GAIN_MUTE (-99999.99dB) as min > > And these three are for hardware that use it as a plain multiplier. > > All the others seem to be mistakes: > >> soc/codecs/stac9766.c:static const DECLARE_TLV_DB_LINEAR(master_tlv, -4600, 0); >> soc/codecs/stac9766.c:static const DECLARE_TLV_DB_LINEAR(record_tlv, 0, 2250); >> soc/codecs/stac9766.c:static const DECLARE_TLV_DB_LINEAR(beep_tlv, -4500, 0); >> soc/codecs/stac9766.c:static const DECLARE_TLV_DB_LINEAR(mix_tlv, -3450, 1200); > > These are wrong, both the AC'97 spec and the STAC9766 datasheet say > that there is a linear register value/dB mapping; these should all use > DECLARE_TLV_DB_SCALE. > >> soc/codecs/wm8350.c:static DECLARE_TLV_DB_LINEAR(pre_amp_tlv, -1200, 3525); >> soc/codecs/wm8350.c:static DECLARE_TLV_DB_LINEAR(out_pga_tlv, -5700, 600); > > According to the datasheet, these should use DECLARE_TLV_DB_SCALE (like > all the others in this file). > >> soc/codecs/wm8400.c:static const DECLARE_TLV_DB_LINEAR(rec_mix_tlv, -1500, 600); >> soc/codecs/wm8400.c:static const DECLARE_TLV_DB_LINEAR(in_pga_tlv, -1650, 3000); >> soc/codecs/wm8400.c:static const DECLARE_TLV_DB_LINEAR(out_mix_tlv, -2100, 0); >> soc/codecs/wm8400.c:static const DECLARE_TLV_DB_LINEAR(out_pga_tlv, -7300, 600); >> soc/codecs/wm8400.c:static const DECLARE_TLV_DB_LINEAR(out_omix_tlv, -600, 0); >> soc/codecs/wm8400.c:static const DECLARE_TLV_DB_LINEAR(out_dac_tlv, -7163, 0); >> soc/codecs/wm8400.c:static const DECLARE_TLV_DB_LINEAR(in_adc_tlv, -7163, 1763); >> soc/codecs/wm8400.c:static const DECLARE_TLV_DB_LINEAR(out_sidetone_tlv, -3600, 0); >> soc/codecs/wm8400.c: 0,7, TLV_DB_LINEAR_ITEM(-1200, 600), >> soc/codecs/wm8990.c:static const DECLARE_TLV_DB_LINEAR(rec_mix_tlv, -1500, 600); >> soc/codecs/wm8990.c:static const DECLARE_TLV_DB_LINEAR(in_pga_tlv, -1650, 3000); >> soc/codecs/wm8990.c:static const DECLARE_TLV_DB_LINEAR(out_mix_tlv, 0, -2100); >> soc/codecs/wm8990.c:static const DECLARE_TLV_DB_LINEAR(out_pga_tlv, -7300, 600); >> soc/codecs/wm8990.c:static const DECLARE_TLV_DB_LINEAR(out_omix_tlv, -600, 0); >> soc/codecs/wm8990.c:static const DECLARE_TLV_DB_LINEAR(out_dac_tlv, -7163, 0); >> soc/codecs/wm8990.c:static const DECLARE_TLV_DB_LINEAR(in_adc_tlv, -7163, 1763); >> soc/codecs/wm8990.c:static const DECLARE_TLV_DB_LINEAR(out_sidetone_tlv, -3600, 0); >> soc/codecs/wm8990.c: 0, 7, TLV_DB_LINEAR_ITEM(-1200, 600), > Could this maybe explain why pulseaudio was having such problems with alsa with regards to gain controls???? _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
