57 lines
1.3 KiB
Text
57 lines
1.3 KiB
Text
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#lang scribble/manual
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@(require (for-label racket))
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@title{SpecCentroid}
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Spectral centroid@section{categories}
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UGens>FFT
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@section{related}
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Classes/SpecFlatness, Classes/SpecPcile
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@section{description}
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Given an link::Classes/FFT:: strong::chain::, this measures the emphasis::spectral:: centroid, which is the weighted mean frequency, or the "centre of mass" of the spectrum. (DC is ignored.)
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This can be a useful indicator of the perceptual emphasis::brightness:: of a signal.
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@section{classmethods}
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@section{method}
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kr
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@section{argument}
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buffer
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an link::Classes/FFT:: chain.
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@section{examples}
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A link::Classes/Blip:: oscillator is ideal for demonstrating this because the number of harmonics is directly manipulated: as the number of harmonics increases, the centroid is pushed higher. In the example, left-to-right changes the number of harmonics, but up-to-down changes the fundamental pitch; note the different effects of these two on the centroid.
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@racketblock[
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s.boot;
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b = Buffer.alloc(s,2048,1);
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(
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x = {
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var in, chain, freq, rq, centroid;
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//freq = LFPar.kr(0.3).exprange(100, 1000);
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freq = MouseY.kr(1000, 100, 1);
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in = Blip.ar(freq, MouseX.kr(1, 100, 1));
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chain = FFT(b, in);
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centroid = SpecCentroid.kr(chain);
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Out.ar(0, in.dup * 0.1);
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centroid.poll(10);
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}.play(s);
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)
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x.free;
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::
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]
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