Ian Scott ian@polpo.org wrote:
Unfortunately, if it's a 20-bit DAC and you feed it 24 bits of data, the 4 least signifigant bits just get chopped off which is not desirable. I would venture to guess that 16 bits with MAD's dithering would be better than 24 bits with the last 4 being ignored.
A slightly strange thing to venture....
Truncating 24bit data after 20 bits would give an effective 19.5 bits, _across the entire frequency range_.
Dithering is about generating a more accurate average value over a range of samples. For example, alternating between two consecutive 16bit values would give an average half way between them i.e. 17bits effective resolution, but only for signals upto 1/4 of the sampling frequency.
To get an effective 20bit output from 16bit samples + dither, you must limit your signals to 1/32 of the sampling frequency (ie 1.4 kHz for 44.1 kHz sampling frequency).
The maths may be slightly more complex than I have made it out to be, but I think the end result is the same: a true 19.5bit output is likely to far superior to 16bit output + dither for almost all types of music.
Andre --
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