/usr/share/puredata/doc/5.reference/fft~-help.pd is in puredata-core 0.46.7-3.
This file is owned by root:root, with mode 0o644.
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#X text 85 158 frequency;
#X floatatom 16 173 0 0 0 0 - - -;
#X obj 16 120 * 44100;
#X floatatom 16 94 0 0 0 0 - - -;
#X text 88 92 frequency;
#X text 91 111 in bins;
#X text 85 175 in Hz.;
#X obj 16 229 osc~;
#X obj 36 16 fft~;
#X obj 86 17 ifft~;
#X text 146 15 - forward and inverse complex FFT;
#X obj 36 42 rfft~;
#X obj 86 43 rifft~;
#X text 146 41 - forward and inverse real FFT;
#X obj 16 254 rfft~;
#X obj 16 148 / 64;
#X obj 574 21 loadbang;
#X msg 574 47 \; pd dsp 1;
#X text 636 403 updated for Pd version 0.33;
#X obj 16 322 rifft~;
#X obj 102 310 print~ real;
#X obj 115 285 print~ imaginary;
#X obj 16 352 /~ 64;
#X obj 16 407 print~ resynthesized;
#X msg 30 380 bang;
#X msg 101 248 bang;
#X msg 100 199 0.25;
#X msg 152 199 0;
#X text 195 200 <-- bash phase;
#X text 152 249 <-- print analysis;
#X text 79 380 <-- print resynthesis;
#X text 76 352 <-- renormalize;
#X text 347 294 There is no normalization \, so that an FFT followed
by an IFFT has a gain of N.;
#X text 346 343 See the FFT examples to see how to use these in practice.
;
#X text 347 205 The real FFT outputs N/2+1 real parts and N/2-1 imaginary
parts. The other outputs are zero. At DC and at the Nyquist there is
no imaginary part \, but the second through Nth output is as a real
and imaginary pair \, which can be thought of as the cosine and sin
component strengths.;
#X text 346 112 The FFT objects do Fourier analyses and resyntheses
of incoming real or complex signals. Complex signals are handled as
pairs of signals (real and imaginary part.) The analysis size is one
block (you can use the block~ or switch~ objects to control block size).
;
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