2010/6/13 Lennart Poettering <mznyfn@xxxxxxxxxxx> > On Thu, 10.06.10 17:11, Colin Guthrie (gmane@xxxxxxxxxxxxxx) wrote: > > > > > 'Twas brillig, and Raymond Yau at 10/06/10 04:16 did gyre and gimble: > > > Can you explain how PA handle the volume controls of ac97 codec ? > > > > > > PCM -34.5dB to +*12* dB > > > Master -46.5dB to 0dB > > > > > > The total dB range (PCM + MASTER) is -81dB to +*12*dB > > > > > > > > > Most user concern about recording without distrotion. (i.e. best result > when > > > Capture Volume at 0dB , PCM and Master Volume at 0dB ) and they need > where > > > are 0dB points > > > > I'm not 100% sure how this is handled, but I know it's not ignored. > > You'll have to ask Lennart directly or dig in the code to see for sure. > > If the ALSA volume range is -x dB to +y dB, then the PA volume range > will be -x-y dB to 0dB (i.e. shifted by -y dB). On top of that most > volume controls should then mark the ALSA 0dB point as "base" volume on > the slider, at what PA then calls -y dB. > > That way we will expose 0dB as maximum hw amplitude uniformly on all > sound cards and have a special point on the slider that is hinted to be > the "comfort" point. > > This is all explained on > http://pulseaudio.org/wiki/WritingVolumeControlUIs#BaseVolumes > shifted +12dB to 0dB is completely wrong +12dB is 4.00 if 0dB is 1.0 (floating point ) you can performed clubsoda 's experiement as in https://bugs.launchpad.net/ubuntu/+source/alsa-driver/+bug/581650 >> "This is important because if I use those maximum settings and play any audio which peaks above -12dB, the output will clip and sound distorted." if your sound card have ac97 codec ., you can use audacity to record the output from hw:0,0 and you will see clipping occur when you set "PCM" volume above 0dB _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
