On Tue, 16 Feb 2010, Lennart Poettering wrote: > On Tue, 16.02.10 09:24, Jaroslav Kysela (perex@xxxxxxxx) wrote: > >>> ALSA 1.0.21 (kernel 2.6.32) added a different TLV type that reports the >>> range with the min/max values to minimize those rounding errors. >> >> Unfortunately, it's not the case of a rounding problem. The USB >> specification is too much vague and vendors don't use the dB range >> correctly. For example, I tested SB MP3+ USB device and reported ranges >> were: >> >> Master: -47.87dB..0.06dB # correct >> Line: 0dB..47.81dB # seems correct -47.81dB..0dB >> Line Capture: -0.18dB..23.81dB # seems correct >> -17.81dB..6.18dB > > Hmm, how did you choose where to put 0dB? It's just tested against another hw using one headphones. >> http://git.alsa-project.org/?p=alsa-kernel.git;a=commitdiff;h=c3a3e040f01457d2ea4f199f75ca205401001a3b >> >> The SB MP3+ uses AC97 codec AD1995 with some own ASIC from Creative. So I >> think that even the 47.87 values are not correct and the real ranges are >> from -48dB..0dB and -18dB..6dB. > > So if I understand this correctly, then the way to handle issues like > this is to measure the dB data for each USB card in question and then > update the drivers with quirks accordingly? Basically, yes, these values should be corrected early as possible. > So if I want my Aureon to work properly I better start measuring now? > > Would it be feasible to allow overriding of the dB data from > userspace, i.e. from the alsa mixer init db perhaps? It's another possibility. But the right place to handle this issue is alsa-lib and parsing a text file with the new data. Jaroslav ----- Jaroslav Kysela <perex@xxxxxxxx> Linux Kernel Sound Maintainer ALSA Project, Red Hat, Inc. _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
