2010/2/17 Eliot Blennerhassett <linux@xxxxxxxxxxxxxxxx> > > > > There are two separate issues here. > 1) Incorrect dB<->linear mapping > ALSA Volume/Gain controls returning incorrect information about mapping > from linear values to dB. E.g. adding "6dB" to the Volume controls > while subtracting 6dB in software does not result in 0dB overall gain. > > For volume controls the convention is 0dB == multiply by 1.0 == no > change. Any sane digital volume control should obey this. > For analog volumes, the 0dB position is entirely arbtrary, as I discuss > below. > > For the alsa db values are in step of 1.5 dB or 3.dB , but the software shift one bit is 10 log 2 = 3.0102996* dB * That 's why adding "6dB" to the Volume controls while subtracting 6dB in software does not result in 0dB overall gain. _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
