111 lines
2 KiB
Text
111 lines
2 KiB
Text
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#lang scribble/manual
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@(require (for-label racket))
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@title{Convolution}
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Real-time convolver.@section{related}
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Classes/Convolution2, Classes/Convolution2L, Classes/Convolution3
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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 of two continuously changing inputs. Also see
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link::Classes/Convolution2:: for a cheaper CPU cost alternative for the
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case of a fixed kernel which can be changed with a trigger message.
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See also link::http://www.dspguide.com/ch18.htm:: by Steven W.
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Smith.
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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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kernel
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Processing kernel.
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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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mul
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Output will be multiplied by this value.
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@section{argument}
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add
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This value will be added to the output.
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@section{Examples}
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@racketblock[
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(
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{ var input, kernel;
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input=SoundIn.ar(0);
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kernel= Mix.ar(LFSaw.ar([300,500,800,1000]*MouseX.kr(1.0,2.0),0,1.0));
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//must have power of two framesize
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Out.ar(0,Convolution.ar(input,kernel, 1024, 0.5));
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}.play;
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)
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(
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//must have power of two framesize- FFT size will be sorted by Convolution 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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s = Server.local;
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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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//random impulse response
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g.set(0,1.0);
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100.do({arg i; g.set(a.rand, 1.0.rand)});
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{ var input, kernel;
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input=SoundIn.ar(0);
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kernel= PlayBuf.ar(1,g.bufnum,BufRateScale.kr(g.bufnum),1,0,1);
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Out.ar(0,Convolution.ar(input,kernel, 2*a, 0.5));
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}.play;
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)
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::
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]
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