>From: Nurkkala Eero.An (EXT-Offcode/Oulu) >Sent: 19 February, 2010 14:58 > >> I'm a bit confused. What do you mean by that? >> >> AFAICS, Q1.14 defines values [-16384.0, +16383.5], which are >mapped in the >> driver to integers [-32768, 32767], right? Moreover, those >Q1.14 values in >> registers are mapped to [-2, 2] in HW. So is there a problem >somewhere? >> >> Cheers, Ilkka > >No, don't get me wrong, not saying there's a problem with the >positive gains, >Q1.14: its range is [-16384.0, +16383.5] = [0x8000, 0x8001 … 0xFFFF, >0x0000, 0x0001 … 0x7FFE, 0x7FFF] >if I read this correctly, your min is 0xFFFF, but the real min maybe >0x8000? To be honest, it may be just me interpreting that incorrectly.. >...as if the value is in two's complement, it goes the opposite: >http://en.wikipedia.org/wiki/Two%27s_complement , see: >1 0 0 0 0 0 0 0 = −128 >1 1 1 1 1 1 1 1 = −1 >what do you think? maybe try it out to see the truth.. Oops, I seemed to copy Q1.14 instead of Q14.1, but isn't it still the same. When I added some debug messages it still seemed to be corret. Lowest number (-32768) is represented with 16th bit '1' and the rest are zeros, right? That is 0x8000. -1 has all the bits set (0xffff) and 0 has all the bit cleared (0x0000). Highest positive value has 16th bit cleared and the rest set (0x7fff). Or did I interpret something wrong? Cheers, Ilkka _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
