2010/6/8 Sebastian H. <vand2@xxxxxx> > > >>>>> I thinks Sebastian's question is whether he can use > >>>>> snd_mixer_selem_set_playback_ > >>>>> dB() set any values in between the volume steps > >>>>> > >>>>> e.g. Master volume control of ac97 is 1.5 dB per step, > >>>>> > >>>>> when using snd_mixer_selem_set_playback_dB() to set -0.9dB , how can > >> the > >>>>> mixer application know what dB value has been set since the value is > in > >>>>> between -1.5dB and 0dB without snd_mixer_selem_get_playbackdB() > >>>> > >>>> Indeed I quite happy with what ALSA already provides (I'm just an > >>>> interested > >>>> amateur). My main problem is that there is no documentation for the > >> Mixer > >>>> API > >>>> and how things are related to each other. Like CTL, HCTL, Mixer and > >>>> SimpleMixer and of course volume and dB in the snd_mixer_selem_ > >> functions. > >>>> > >>>> The root issue is that I wondered if the mixer application should > offer > >> a > >>>> separate text input for decibel values besides the text input for > volume > >>>> values. As pointed out this would not allow for finer grained volume > >>>> control > >>>> therefore for the moment I'll probably stick with a mere text label > for > >> dB. > >>>> > >>>> > >> > >>> The main difference between those volume controls using TLV_DB_SCALE > and > >>> TLV_DB_LINEAR is -6dB is at the middle of TLV_DB_LINEAR and > TLV_DB_SCALE > >> has > >>> fixed dB value between any two steps. > >> > >> What's TLV_DB_SCALE and TLV_DB_LINEAR for? > >> A grep in the alsa-lib sources did not return anything. > >> > >>> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/332631 > >>> > >>> if the user has both hda onboard sound and emu10k1, he may notice that > >> there > >>> is big difference if he set volume at percentage instead of dB > >> > >> Interesting, that's my setup. I have an onboard HDA Intel and a > >> pci SBLive! Card and some el cheapo USB sound cards to experiment > >> with. Thanks I'll give the volume listening test a try at some point. > >> > > > > > > https://bugtrack.alsa-project.org/alsa-bug/view.php?id=4883 > > > > Pekka Lampila reported that when he set -40dB and only get back -9999999 > by > > his program alsa_mixer_test.c > > > > I don't have emu10k1 so don't know whether this is a bug of alsa-lib or > not > > I also get a big jump from -39.60dB to -99999.99 dB for some emu10k1 > sliders when I move them to the minimum although their advertised > minimum is -40dB. This looks like a way to express log ( 0 ). > Do you ream snd_mixer_selem_get_Playback_dB_range() return 40dB but max_dB - min_dB = 99999.99 dB ? _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
