Am 09.06.2010 07:39, schrieb Raymond Yau: > 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 ? e.g. snd_mixer_selem_get_playback_dB_range() for "Wave Surround" returns -40.00 to 0.00 dB and the dB values returned by snd_mixer_selem_get_playback_dB ( elem, SND_MIXER_SCHN_MONO, &_db_value ); are all in this range except for when the volume ist set to 0. At this and only this volume the returned dB value is out of range with -99999.99 dB. For vol=1 the dB value is -39.60. _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
