i tried to dig into fft stuff and read something about it on the pd-tutorial page:
http://pd-tutorial.com/english/ch03s08.html#id432343
in the chapter "folding" (3.8.2.2 Folding) he uses a q8_sqrt~ object for one signal to be folded and for the other one the reciprocal function q8_rsqrt~.
could sombody explain me, why? there's only a short explanation to this patch and i cannot figure out the meaning of the diffent functions for both signals.

Hi,

[q8_sqrt~] is a cpu-friendly alternative for [sqrt~], it does only 8 mantissa bits precision. [q8_rsqrt~] is the reciproce of it, so 1 / sqrt.

In the patch, [q8_rsqrt~] divides the amplitudes by themselves, making all amplitudes 1. [q8_sqrt~] computes the amplitudes of the other signal. Thus, the amplitudes of one signal are replaced by the amplitudes of the second signal, while the original frequencies are preserved. That makes a channel vocoder in frequency domain, no?

Katja