Lennart Poettering wrote: > On Sat, 12.04.08 12:15, James Courtier-Dutton (James@xxxxxxxxxxxxxx) wrote: > > >>> I somehow expected that the magic "0dB" setting in ALSA would refer to >>> some sane default, where the final output would have a sensible >>> volume. In this case this is not so. I am thus wondering how ALSA >>> actually defines 0dB? Is this a bug in the hardware that should be >>> worked around in ALSA? Is this an ALSA bug? >>> > > >> The 0dB is a gain value. >> So 0dB means that the input to the mixer element exactly equals the >> output from the mixer element. >> So 0dB ensures no distortion will occur. >> It is fine to set the 0dB for all output mixer controls except one. >> The problem comes with the "Master" control, where 0dB generally means >> the maximum possible volume. >> > > In the case of the USB speakers there is no Master, only PCM. And it > is that PCM volume that is the offender. > > My I thus assume that we can say that for all but the last element in > the series 0db means avg input power equals avg output power, and for > the last one 0db means max? That would fit on what you are saying but > also match my usb speakers, not depending on the existance of a > "Master". > > >> The correct setting of this is therefore very dependent on the type of >> amplification that is being done after the sound card master output. >> Everyone's setup will vary. But, on my system a value between -40dB and >> -30dB seems about ok. >> The user will hear sound, but it will not be too loud. >> I suppose we will need to canvas people on the best value to use. >> > > With all hw I tested this scheme actually seems to work fine. (-40dB, > Intel HDA, those Logitech speakers, Terratech Aureon 5.1.) > > >> Your report about anything over -41dB is way too loud does present a >> problem. Obviously, the controls for some sound cards are still >> calibrated wrong. Unfortunately, the calibration of USB sound cards is >> not left to ALSA, but in fact the sound card manufacturer sets up the >> calibration tables for us, so for your Logitech speakers, ALSA would >> have to add a specific quirk. >> > > Actually, it is fine with -40dB, not just -41dB. But then it gets > rapidly too loud. > > >> Finally, does anyone else think -40dB for the Master, and 0dB for all >> other controls is too loud for the default or not? >> > > Works fine with my hardware at least ;-) > > My scheme in PA will thus now be: > > 1) Initialize Master to -40dB > 2) If there is no master, initialize PCM to -40dB > 3) If there is a master, initialize PCM to 0dB > > Does that sound reasonable? > > Lennart > > That sounds reasonable for now. Professional sound card users will maybe just have to remember to mute the master control before connecting their speakers. I don't understand why your sound card is OK at -40dB but too loud at -41dB. It does not make any sense. There must be a bug there, because -41dB should be quieter than -40dB. James _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
