On Sun, Jun 08, 2014 at 12:36:17PM +0200, hermann meyer wrote:
> Without downsampling it use (well, 4xtimes more then now) 8% dsp
because that removes most of the broadband junk that would be generated
> and for guitar/bass 3kHz are
True for bass and guitar.
Still this algorithm is far from what it could be. I don't blame
for you that, it's Bernsee who is missing the consequences of his
own analysis (which is valid as far as it goes).
Take alook at his table labeled 'pass #5'. The input signal is
halfway between two bins. Assume we want one octave up. The expected
output signal corresponds exactly to bin 225. For that signal, the
output of the analysis FFT would be (similar to 'pass #1):
And that is of course also what the correct input to the synthesis
IFFT should be. Which is quite different from what the algorithm
produces (by scaling each bin individually):
The result of this after the IFFT is the correct frequency, but
with two periods of the window applied (it will be zero at the
The frequency values that are calculated provide exactly the
information required to avoid this and to do the correct
calculation. But it's just thrown away.
A world of exhaustive, reliable metadata would be an utopia.
It's also a pipe-dream, founded on self-delusion, nerd hubris
and hysterically inflated market opportunities. (Cory Doctorow)
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