On Wed, 17.02.10 11:30, Raymond Yau (superquad.vortex2@xxxxxxxxx) wrote: > > 2010/2/16 Lennart Poettering <mznyfn@xxxxxxxxxxx> > > > On Tue, 16.02.10 09:08, Clemens Ladisch (clemens@xxxxxxxxxx) wrote: > > > > > > > > Lennart Poettering wrote: > > > > Getting back to the invalid dB data from the USB cards: the question > > > > is whether the USB descriptor data is badly parsed, and the dB > > > > mismatch hence systematic for USB cards, > > > > > > USB descriptors use units of 1/256th dB, while ALSA uses 1/100th dB. > > > When the level is computed from the minimum plus a multiple of the step > > > size, rounding errors add up considerately. > > > > > > 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. > > > > I am really sure that the discrepancy I measure with the Aureon is way > > beyond rounding errors. > > > > Lennart > > > > > if the program use a format FLOAT_LE which is not supported by the hardware > and need to use plughw , you have already added error ( resampling and > format conversion ) to the result That numeric noise is neglible in contrast to the big (20dB or so?) discrepancy I am seeing here. Lennart -- Lennart Poettering Red Hat, Inc. lennart [at] poettering [dot] net http://0pointer.net/lennart/ GnuPG 0x1A015CC4 _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
