[LAD] SysEx data-conversion woes: nibbles and complements (Microwave 2)

Jeanette C. julien at mail.upb.de
Thu May 13 21:27:57 CEST 2021

May 13 2021, Fons Adriaensen has written:
> FFT theory will provide
> a solution. If you want to think about it, I can give you two hints:
> * It's related to the sin() vs. cos() thing mentioned earlier.
> * In this particular case there's an extra twist to it - think
>  of shifting a cyclic waveform in time by half a sample.
Could it be as simple, as bluntly put: forget about the phase, only use
the amplitude/overall power of any harmonic from an FFT and reconstrcut
the signal from all sines at 0 phase?

I tried a simple experiment in Csound and sonically it didn't make much
of a difference. Though my experiment was quite basic: sines on every
odd harmonic, cosines on every even and then shift the cosine part
around. Audible in direct comparison. Noticeable, of course, in
amplitude, but still very similar. And it would fulfill the half-cycle
criterion wave[64+n] = -wave[64-n]
I suppose one could be a little less crude and look at the phase and
round to 0 or 180 degrees.

Am I close or completely off the track, still?

Best wishes,


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