At Fri, 03 Dec 2010 16:34:14 +0100, David Henningsson wrote: > > On 2010-12-03 12:59, Takashi Iwai wrote: > > At Fri, 03 Dec 2010 12:30:02 +0100, > > David Henningsson wrote: > >> > >> I'm trying to nail down a strange behaviour. I have one "Master" and one > >> "Speaker" (or "Headphone") volume control, each ranging from -48 dB to 0 > >> dB. Whenever the sum of "Master" and "Speaker" is below -48 dB, the > >> output mutes. Codec is attached. > >> > >> "Master" is a "Virtual master" control, and both "Master" and "Speaker" > >> control amp-out on nid 0x13. Nid 0x13 does not have amp-out caps, but > >> the AFG specifies a range of -96 dB to 0 dB in 0.75 dB steps. > >> > >> There is some strange things here. First, in > >> patch_sigmatel:create_controls_idx, there is this comment: > >> > >> /* if dB scale is over -64dB, and finer enough, > >> * let's reduce it to half > >> */ > >> Hmm? Removing half of the volume slider? > >> > >> Second, assuming we actually buy this decision, wouldn't it make sense > >> for people to be able to combine Master and Speaker to get the full -96 > >> to 0 dB range? Instead, "Master" is just working over the range defined > >> by "Speaker". > > > > Well, the problem was fairly old. You must think of the world before > > anything dB evaluation was introduced in the mixer apps. They just > > took a percentage value, so we got to cut it off to give some "usable" > > interface for them. > > > > The biggest problem right now is that you can't take it back so easily > > "just for PA". The PCM softvol is also the same. There is no perfect > > solution, and PA isn't by 100% people here. However, we must not give > > a regression in 100% manner. > > Ok. I'm not certain I agree, but I see your point. > > > > > OK, let's back to the bug point... > > > >> Third, there is an interesting condition in hda_codec.c:update_amp_value: > >> > >> if (val> 0) > >> val += ofs; > >> > >> Now this is in practice turning all volume controls which have ofs (e g > >> those being "reduced to half") to a minimum-is-mute error: I can set the > >> amp value to either 0 (-96 dB) or the 65 - 127 range (~ -48 dB - 0 dB). > >> So it isn't really mute, it's -96 dB signal, but I can't hear that anyway. > > > > OK, this looks really like a bug that the driver gives min-mute flag. > > The min-mute flag should be given only for the STAC codecs with lower > > resolution, such as STAC9200. It seems that STAC925x (and STAC9202) > > are also in this category, while STAC9205 and other IDT codecs have > > higher resolutions. > > > > Since both STAC9200 and STAC925x have own Master definition, the > > simplest solution is to remove TLV_DB_SCALE_MUTE for vmaster like > > below... > > I've tried it, but it doesn't help. Test case is simple: run the codec > attached to the previous mail in hda-emu [1]. Then turn "Master" down > from 64 to 60, or anything that makes the combination of "Master" and > "Speaker" less than -48 dB, and notice that the amp value sent to the > codec is 0x0 (i e -96 dB). Ah, it's vmaster that limits the min/max in the upper layer. In the current code, 0 is always handled as 0 in update_amp_value(), so this is the case. Fixing it would be tricky. The easiest way is to reduce this cut-off, but then it will hit too many people. > [1] If I never thanked you for that program, I do so now, it is a really > great tool! Good to hear :) thanks, Takashi _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
