pd-cyclone 0.1~alpha55-3 / usr / lib / pd / extra / cyclone / svf~-help.pd

#N canvas 1281 327 924 425 10;
#X declare -lib cyclone;
#X obj 407 306 dac~;
#N canvas 324 234 556 460 svf_part2 0;
#X text -1 306 onepole~.help contains yet another example.;
#X text -1 382 svf~ accepts arguments or max messages to change the
frequency input mode. it is generally recommended to set the mode with
an argument and leave it constant \, to avoid confusion.;
#X text -1 244 try sweeping the cutoff frequency in linear mode \,
then in radians mode \, to appreciate the difference. a similar principle
operates in the amplitude domain \, where exponential audio faders
are used to match our logarithmic perception of loudness.;
#X text -51 134 linear;
#X text -27 81 Hz;
#X text -1 177 in this mode \, input values from (0 -> 1) are interpreted
as radians \, producing a quarter-cycle sinusoidal mapping to cutoff
frequencies. this conforms the frequency mapping to a response that
is closer to our logarithmic perception of pitch.;
#X text -1 125 this mode is essentially the same \, but with a normalized
input range. linear input values from (0 -> 1) are mapped to cutoff
frequencies in the effective range \, (0 -> fs/4).;
#X text -1 72 this is the default mode. input values set the cutoff
frequency directly. therefore \, the input range is the same as the
cutoff frequency (0 -> fs/4) \, and response is linear.;
#X text -1 9 svf~ has three different modes for mapping input values
onto cutoff frequency. these are mainly for convenience \, but they
may also improve efficiency slightly.;
#X text -1 329 since svf~ only samples its control inputs once per
vector \, it is more efficient to use the radians mode than to do logarithmic
scaling outside the object at audio rate.;
#X text -59 191 radians;
#X restore 617 344 pd svf_part2;
#X text 16 12 state-variable filter;
#X text 8 273 special thanks to 2up;
#X msg 379 81 0.5;
#X text 545 118 frequency range is 0 - f(s)/4;
#X obj 409 151 noise~;
#X text 8 158 Floats or signals can modify these in real-time. The
value of these parameters is only sampled once per signal vector.;
#X text 8 138 Arguments are cutoff frequency (Hz) \, and resonance
(0-1).;
#X text 8 93 One of its advantages is that the it produces low-pass
\, high-pass \, band-pass \, and band-reject (notch) output simultaneously
- so all four are available in parallel.;
#X text 8 65 svf~ implements Chamberlin's state-variable filter algorithm.
;
#X msg 422 86 37;
#X text 553 164 left: (signal) filter input;
#X text 527 254 outputs: lowpass \, highpass \, bandpass \, notch;
#X text 553 192 right: (signal/float) resonance (0 - 1);
#X text 553 178 middle: (signal/float) cutoff frequency;
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#X floatatom 458 127 0 0 0 0 - - -;
#N canvas 40 55 716 389 svf_algorithm 0;
#X text 242 290 bandstop = lowpass + hipass \;;
#X text 59 179 this is the dsp loop. note how the calculations work
together to produce all four outputs simultaneously.;
#X text 62 123 first \, convert hz to radians (this step is not necessary
in radians input mode);
#X text 44 82 this is the basic algorithm inside svf~:;
#X text 237 137 cf_radians = sin(2. * PI * cf_hz * x->ifs) \;;
#X text 242 258 bandpass = bandpass + cf_radians * hipass \;;
#X text 242 242 hipass = in_samp - lowpass - q * bandpass \;;
#X text 242 226 lowpass = lowpass + (cf_radians * bandpass) \;;
#X text 242 274 bandpass = bandpass - (bandpass ^ 3.) * 0.0001 \;;
#X restore 499 344 pd svf_algorithm;
#X text 8 240 (float) resonance (0-1);
#X text 8 226 (float) cutoff frequency (Hz);
#X text 8 212 arguments (optional):;
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#X obj 508 219 *~ 0;
#X obj 475 219 *~ 0;
#X obj 442 219 *~ 0;
#X obj 409 219 *~ 0;
#X floatatom 507 151 0 0 0 0 - - -;
#X obj 498 12 import cyclone;
#X obj 409 175 svf~ 797 0.5;
#X obj 409 269 *~ 0.7;
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