puredata-doc 0.47.1-3 / usr / share / puredata / doc / 3.audio.examples / I02.Hann.window.pd

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#X msg 31 411 \; pd dsp 1;
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#X text 225 131 tabreceive~ outputs array contents \,;
#X text 225 149 constantly \, every block. Here it's;
#X text 223 169 used to get the Hann window to;
#X text 225 187 multiply by the input.;
#X text 120 7 block~ object does no computation but declares this;
#X text 120 24 window to be operating at a different block size from
;
#X text 122 58 Fourier transform.;
#X text 121 40 the parent window. This determines the size of the;
#X text 76 99 The inlet~ automatically re-blocks to the new block size.
;
#X obj 15 332 +~;
#X text 94 308 Take the magnitude by squaring real and imaginary part
\, adding and taking square root.;
#X text 110 424 periodically graph the output. It appears every 512
samples (about 12 milliseconds) but we only update the graph 4 times
per second. The graph is back on the main (parent) window.;
#X text 82 215 forward real FFT. Like "fft~" \, but only one inlet
(for the real part) and only the first half of the output signals are
used. (The others are determined by symmetry: they're complex conjugates
of the first half \, in reverse order.) This takes 1/2 the CPU time
of "fft".;
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#X text 110 6 WINDOWING AND BLOCKING FOURIER TRANSFORMS;
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#X text 305 559 updated for Pd version 0.39;
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#X text 383 378 Hann window;
#X text 98 462 period 512;
#X text 40 368 recalculate Hann;
#X text 75 383 window table;
#X text 100 233 tens of Hz.;
#X text 80 215 <- frequency \,;
#X text 98 270 click here and;
#X text 170 286 <- see;
#X text 21 32 In this example we use a sub-patch ("pd fft-analysis")
to re-block the Fourier transform to 512 points. The signal is multiplied
by the Hann window function (which is just a raised cosine.) The magnitude
\, which is computed in the sub-patch \, is graphed below in this window.
The point at 255 corresponds to just below the Nyquist frequency. Phase
isn't shown \, and unlike the previous patch we don't control the initial
phase of the oscillator. (For fun \, try drawing other window functions
with the mouse...);
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