2010/2/17 Jaroslav Kysela <perex@xxxxxxxx> > On Tue, 16 Feb 2010, Lennart Poettering wrote: > > > On Tue, 16.02.10 14:40, Mark Brown (broonie@xxxxxxxxxxxxxxxxxxxxxxxxxxx) > wrote: > > > >> > >> On Tue, Feb 16, 2010 at 03:32:01PM +0100, Lennart Poettering wrote: > >>> On Tue, 16.02.10 09:24, Jaroslav Kysela (perex@xxxxxxxx) wrote: > >> > >>>> Line: 0dB..47.81dB # seems correct -47.81dB..0dB > >>>> Line Capture: -0.18dB..23.81dB # seems correct > >>>> -17.81dB..6.18dB > >> > >>> Hmm, how did you choose where to put 0dB? > >> > >> The Line one looks like someone got attenuation and gain confused, which > >> is a fairly common mistake for people to make when copying information > >> from one place to another. Possibly a similar thing going on with the > >> Line Capture control, plus a fixed 6dB gain (which may well be a > >> separate amp...). > > > > I remember that a while back we had a discussion on alsa-devel > > regarding the fact that ALSA does not define relative to what the dB > > values reported by the mixer elements actually are measured. Some > > mixer controls export dB values relative to max amplification (e.g. my > > integrated USB speakers here), others relative to the output of some > > other mixer element, and others relative to different standard or > > not-so-standard output voltages. And there is no API to figure out > > what the base is. > > > > Now, what Jaroslav listed above suggests that he chose carefully where > > he put 0dB. I was just wondering about that. Jaroslav, how did you > > choose where to put 0dB? > > Basically, if I remember correctly the discussion, 0dB on all elements > should main unchanged volume, <0dB attenuation and >0dB gain. We cannot > measure precisely other components on path like analog volume wheels > (like SB MP3+ has to change line-out volume), analog amplifiers and other > analog signal modificators. > > So, if you use one headphones and speakers with defined and fixed volume > settings, you can measure differences for the card with broken dB volume > ranges. I just used another HDA card in notebook with 0dB settings on all > playback controls on path, captured stream from this card on my USB card > and played this stream back on my USB card watching and relating the > volume levels according dB values. It's not 100% correct, but at least > it's something to start with. > > Jaroslav > <Alsa-devel@xxxxxxxxxxxxxxxx> > Refer to http://thread.gmane.org/gmane.linux.alsa.devel/15859 Try to lower "Wave" volume - otherways there will be clipping on bass. When you set "PCM" to 75 % this is 0 db. The dB scale of alsa driver was implemented because of 0dB is not at the maximum for emu10k1 _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
