141 lines
3.5 KiB
Racket
141 lines
3.5 KiB
Racket
#lang scribble/manual
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@(require (for-label racket))
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@title{PartConv}
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Real-time partitioned convolution@section{categories}
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UGens>FFT, UGens>Convolution
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@section{related}
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Classes/Convolution, Classes/Convolution2, Classes/Convolution2L, Classes/Convolution3
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@section{description}
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Partitioned convolution. Various additional buffers must be supplied.
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Mono impulse response only! If inputting multiple channels, you'll need independent PartConvs, one for each channel.
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But the charm is: impulse response can be as large as you like (CPU load increases with IR size. Various tradeoffs based on fftsize choice, due to rarer but larger FFTs. This plug-in uses amortisation to spread processing and avoid spikes).
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Normalisation factors difficult to anticipate; convolution piles up multiple copies of the input on top of itself, so can easily overload.
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@section{classmethods}
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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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fftsize
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spectral convolution partition size (twice partition size). You must ensure that the blocksize divides the partition size and there are at least two blocks per partition (to allow for amortisation).
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@section{argument}
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irbufnum
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prepared buffer of spectra for each partition of the inpulse response.
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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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// preparation; essentially, allocate an impulse response buffer, then follow a special buffer preparation step to set up the data the plugin needs. Different options are provided commented out for loading impulse responses from soundfiles.
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(
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~fftsize=2048; // also 4096 works on my machine; 1024 too often and amortisation too pushed, 8192 more high load FFT
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s.waitForBoot({
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{
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var ir, irbuffer, bufsize;
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// // MONO ONLY
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// pre-existing impulse response sound files
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// (could also use any general soundfile too for cross-synthesis effects)
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// irbuffer= Buffer.read(s, "/Volumes/data/audio/ir/ir2.wav");
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// irbuffer= Buffer.read(s, "/Volumes/data/audio/ir/ir.wav");
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// this is a two second long hall IR
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// irbuffer= Buffer.read(s, "/Volumes/data/audio/ir/bighall2.wav");
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// synthesise the honourable 'Dan Stowell' impulse response
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ir = ([1] ++0.dup(100) ++ ((1, 0.99998 .. 0).collect{|f| f =
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f.squared.squared; f = if(f.coin){0}{f.squared}; f =
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if(0.5.coin){0-f}{f} } * 0.1)).normalizeSum;
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// ir.plot;
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irbuffer = Buffer.loadCollection(s, ir);
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s.sync;
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bufsize= PartConv.calcBufSize(~fftsize, irbuffer);
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// ~numpartitions= PartConv.calcNumPartitions(~fftsize, irbuffer);
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~irspectrum= Buffer.alloc(s, bufsize, 1);
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~irspectrum.preparePartConv(irbuffer, ~fftsize);
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s.sync;
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irbuffer.free; // don't need time domain data anymore, just needed spectral version
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}.fork;
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});
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)
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~target= Buffer.read(s, Platform.resourceDir +/+ "sounds/a11wlk01.wav");
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// ~target= Buffer.read(s, "sounds/break");
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(
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{ var input, kernel;
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input= PlayBuf.ar(1, ~target, loop:1);
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Out.ar(0, PartConv.ar(input, ~fftsize, ~irspectrum.bufnum, 0.5));
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}.play;
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)
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// convolve with live input
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(
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{ var input, kernel;
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input= SoundIn.ar(0);
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Out.ar(0, PartConv.ar(input, ~fftsize, ~irspectrum.bufnum));
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}.play;
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)
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// should get back original impulse response (once every four seconds)
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(
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{ var input, kernel;
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input= Impulse.ar(0.25);
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Out.ar(0, PartConv.ar(input, ~fftsize, ~irspectrum.bufnum));
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}.play;
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)
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// only free buffers once you're finished with examples
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// if you free whilst PartConv is still running, the server won't crash, but PartConv output will go to zero abruptly
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(
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~irspectrum.free;
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~target.free;
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currentEnvironment.clear;
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)
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::
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]
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