[alsa-devel] wrong decibel data?

Raymond Yau superquad.vortex2 at gmail.com
Sun Apr 4 03:31:42 CEST 2010

2010/4/3 Colin Guthrie <gmane at colin.guthr.ie>

> 'Twas brillig, and Nicolo' Chieffo at 02/04/10 21:25 did gyre and gimble:
> > I just had a discussion with pulseaudio developers in which they told
> > me that if the speakers don't emit any audio when the ALSA volume is
> > 0%, then the correct gain value should be -inf dB (a value lower than
> > -200 for pulseaudio means mute). Unfortunately my card has -48 dB.
> >
> > They also said that if with -47.25 dB (which is what I get with ALSA
> > volume set to 2%) I can hear audio even if it's very very low, at -48
> > dB I should still be able to hear something (the scale is
> > logarithmic).
> >
> > Their request is to change to -200 the gain reported from my card
> > driver when the ALSA volume is set to 0%.
> > Thanks
> FWIW, I've got the same/similar h/w with a cutoff at 14% in PA as you
> have. I've been meaning to get this fixed for a while, but I'm
> incredibly lazy with certain things that don't bother me practically, so
> haven't followed it up yet.
> Thanks for getting the ball rolling :)
> If any specific debug is needed here, feel free to ask.
> Col
> --

since PA provide software atten/software gain ,the software atten of 16bits
audio is -48dB

I guess the problem is related to PA shift the 0dB point (i.e. the software
gain +15dfB to 0dB)

you have to ask PA developer the value of software dB gain provided by the
PA server

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