puredata-doc 0.47.1-3 / usr / share / puredata / doc / 3.audio.examples / J09.bandlimited.pd

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#X text 208 45 band limit (MIDI units);
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#X text 75 15 BAND-LIMITED SAWTOOTH GENERATOR USING A TRANSITION TABLE
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#X text 39 657 Now any time we wish to make a discontinuity in the
output signal \, we make it look exactly like the bandlimited square
wave looks. We do this by reading through the table we recorded \,
carefully adding a "digital" \, non-band-limited \, sawtooth to "array1"
so that the discontinuities in the two cancel out and what you have
left is the transition in the table.;
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#X text 242 138 back the phase up one sample;
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#X text 292 216 twice the table length;
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#X text 80 369 This one is used - first and third harmonics only.;
#X text 28 644 This alternate one puts in harmonics 1 \, 3 \, and 5
;
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#X text 537 179 ----- 1002 samples ----;
#X text 24 27 This network puts a half cycle of a band-limited square
wave into the table "array1.";
#X text 22 64 Logically the half-cycle is in samples 1 through 1000
\; samples 0 and 1001 are provided so that the 4-point interpolation
will work everywhere.;
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#X text 351 853 updated for Pd version 0.39;
#X text 37 515 A more sophisticated way to control foldover in sawtooth
waves is to replace the once-a-cycle jump with a bandlimited transition.
To get a band-limited transition we synthesize a band-limited square
wave and harvest the transition from the middle of the top half to
the middle of the bottom half. Here we use a square wave at SR/10 \,
so that only partials 1 and 3 fit below the Nyquist. The transition
should take 1/2 period \, or 5 samples. The table is calculated and
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#X text 40 767 The "band limit" controls how fast the transition table
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0.4 times the Nyquist \, or five samples a cycle. Lowering the band
limit cuts off the partials of the generated sawtooth wave at frequencies
below the Nyquist.;
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