220 lines
4.3 KiB
Racket
220 lines
4.3 KiB
Racket
#lang scribble/manual
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@(require (for-label racket))
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@title{Convolution2L}
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Real-time convolver with linear interpolation@section{related}
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Classes/Convolution, Classes/Convolution2, Classes/Convolution3, Classes/StereoConvolution2L
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@section{categories}
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UGens>FFT, UGens>Convolution
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@section{description}
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Strict convolution with fixed kernel which can be updated using a trigger signal. There is a linear crossfade between the buffers upon change.
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See emphasis:: Steven W Smith, The Scientist and Engineer's Guide to Digital Signal Processing: chapter 18:: -
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http://www.dspguide.com/ch18.htm
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@section{classmethods}
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@section{private}
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categories
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@section{method}
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ar
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@section{argument}
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in
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processing target
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@section{argument}
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kernel
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buffer index for the fixed kernel, may be modulated in combination with the trigger
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@section{argument}
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trigger
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update the kernel on a change from <=0 to >0
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@section{argument}
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framesize
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size of FFT frame, must be a power of two (512, 1024, 2048, 4096 are standard choices).
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Convolution uses twice this number internally.
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Note that the convolution gets progressively more expensive to run for higher powers!
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The maximum value you can use is 2^16=16384.
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(This upper limit is half of "SC_FFT_MAXSIZE" defined in the SC source code.)
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Larger convolutions than this can be done using link::Classes/PartConv::.
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@section{argument}
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crossfade
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The number of periods over which a crossfade is made. The default is 1. This must be an integer.
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@section{argument}
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mul
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@section{argument}
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add
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@section{Examples}
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@racketblock[
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(// allocate three buffers
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b = Buffer.alloc(s, 2048);
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c = Buffer.alloc(s, 2048);
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d = Buffer.alloc(s, 2048);
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b.zero;
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c.zero;
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d.zero;
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)
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(
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50.do({ |it| c.set(20*it+10, 1.0.rand); });
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3.do({ |it| b.set(400*it+100, 1); });
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20.do({ |it| d.set(40*it+20, 1); });
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)
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::
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]
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@racketblock[
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(
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SynthDef(\conv_test, { arg kernel, t_trig=0;
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var input;
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input=Impulse.ar(1);
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// must have power of two framesize
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Out.ar(0, Convolution2L.ar(input, kernel, t_trig, 2048, 1, 0.5));
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}).add
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)
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x = Synth(\conv_test, [\kernel, b]);
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// changing the buffer number:
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x.set(\kernel, c);
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x.set(\t_trig, 1); // after this trigger, the change will take effect.
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x.set(\kernel, d);
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x.set(\t_trig, 1); // after this trigger, the change will take effect.
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d.zero;
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40.do({ |it| d.set(20*it+10, 1); });// changing the buffers' contents
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x.set(\t_trig, 1); // after this trigger, the change will take effect.
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x.set(\kernel, b);
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x.set(\t_trig, 1); // after this trigger, the change will take effect.
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x.free;
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::
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]
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@racketblock[
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// longer crossfade
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(
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SynthDef( \conv_test2, { arg kernel, t_trig=0;
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var input;
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input=Impulse.ar(1);
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// must have power of two framesize
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Out.ar(0, Convolution2L.ar(input, kernel, t_trig, 2048, 5, 0.5));
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}).add
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)
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x = Synth(\conv_test2, [\kernel, b]);
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// changing the buffer number:
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x.set(\kernel, c);
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x.set(\t_trig, 1); // after this trigger, the change will take effect.
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x.set(\kernel, d);
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x.set(\t_trig, 1); // after this trigger, the change will take effect.
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d.zero;
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40.do({ |it| d.set(20*it+10, 1); });// changing the buffers' contents
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x.set(\t_trig, 1); // after this trigger, the change will take effect.
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x.set(\kernel, b);
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x.set(\t_trig, 1); // after this trigger, the change will take effect.
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x.free;
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::
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]
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@racketblock[
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// next example
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b = Buffer.read(s, Platform.resourceDir +/+ "sounds/a11wlk01.wav");
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(
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{ var input, kernel;
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input= SoundIn.ar(0);
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// must have power of two framesize
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Convolution2L.ar(input, b, 0, 512, 1, 0.5);
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}.play;
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)
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::
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]
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@racketblock[
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// another example
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(
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// must have power of two framesize- FFT size will be sorted by Convolution2 to be double this
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// maximum is currently a=8192 for FFT of size 16384
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a=2048;
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// kernel buffer
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g = Buffer.alloc(s, a, 1);
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)
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(
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g.set(0, 1.0);
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100.do({arg i; g.set(a.rand, (i+1).reciprocal)});
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)
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(
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// random impulse response
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{
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var input, inputAmp, threshhold, gate;
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input = SoundIn.ar(0);
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inputAmp = Amplitude.kr(input);
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threshhold = 0.02; // noise gating threshold
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gate = Lag.kr(inputAmp > threshhold, 0.01);
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Convolution2L.ar(input*gate, g, 0, a, 1, 0.5);
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}.play;
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)
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::
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]
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@racketblock[
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// one last example
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(
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b = Buffer.alloc(s, 512, 1);
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b.sine1(1.0/[1, 2, 3, 4, 5, 6], true, true, true);
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)
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(
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{ var input, kernel;
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input=SoundIn.ar(0);
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// must have power of two framesize
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Convolution2L.ar(input, b, 0, 512, 1, 0.5);
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}.play;
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)
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::
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]
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