On Wed, 30 Aug 2017 21:48:58 +0200, Jack Bates wrote: > > I confirmed with Wireshark that my USB sound card responds to GET_MIN > with 0x0000 and GET_MAX with 0x6300 .. The audio device class > definition [1] says the units are 1/256 dB (section 5.2.2.2.3: Mixer > Control) ... So by my calculation, the min and max are 0 and 99 dB > (0x6300 / 256 == 99) ... Why then does alsactl print: > > > range '0 - 99' > > dbmin 0 > > dbmax 38 > > (/usr/sbin/aslactl -f - store) > > I originally asked about this on the pulseaudio-discuss list [2] > because it uses "dB data" [3]. > > The "0 - 99" makes sense -- it lines up with my calculation ... Where > does the 38 come from? (I expect it's obvious, I just haven't found > the explanation?) Hm, what shows /proc/asound/card*/usbmixer proc file? It contains some raw data. Basically the driver simply interprets the USB descriptor min/max unless there are overriding mappings by quirk list. Takashi _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
