124 lines
2.6 KiB
Text
124 lines
2.6 KiB
Text
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#lang scribble/manual
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@(require (for-label racket))
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@title{PV_HainsworthFoote}
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FFT onset detector.@section{related}
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Classes/PV_JensenAndersen
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@section{categories}
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UGens>FFT
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@section{description}
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FFT onset detector based on work described in emphasis:: Hainsworth, S. (2003) Techniques for the Automated Analysis of Musical Audio. PhD, University of Cambridge engineering dept. ::
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See especially p128. The Hainsworth metric is a modification of the Kullback Liebler
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distance.
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The onset detector has general ability to spot spectral change, so may
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have some ability to track chord changes aside from obvious transient
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jolts, but there's no guarantee it won't be confused by frequency
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modulation artifacts.
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Hainsworth metric on it's own gives good results but Foote might be
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useful in some situations: experimental.
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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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buffer
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FFT buffer.
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@section{argument}
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proph
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What strength of detection signal from Hainsworth metric to use.
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@section{argument}
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propf
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What strength of detection signal from Foote metric to use. The
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Foote metric is normalised to (0..1).
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@section{argument}
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threshold
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Threshold hold level for allowing a detection.
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@section{argument}
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waittime
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If triggered, minimum wait until a further frame can cause
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another spot (useful to stop multiple detects on heavy signals).
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@section{Examples}
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@racketblock[
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//just Hainsworth metric with low threshold
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(
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SynthDef(\fftod, {
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var source1, detect;
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source1= AudioIn.ar(1);
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detect= PV_HainsworthFoote.ar(FFT(LocalBuf(2048),source1), 1.0, 0.0);
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Out.ar(0,SinOsc.ar([440,445],0,Decay.ar(0.1*detect,0.1)));
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}).play(s);
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)
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//spot note transitions
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(
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SynthDef(\fftod, {
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var source1, detect;
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source1= LFSaw.ar(LFNoise0.kr(1,90,400),0,0.5);
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detect= PV_HainsworthFoote.ar(FFT(LocalBuf(2048),source1), 1.0, 0.0, 0.9, 0.5);
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Out.ar(0,Pan2.ar(source1,-1.0)+ Pan2.ar(SinOsc.ar(440,0,Decay.ar(0.1*detect,0.1)),1.0));
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}).play(s);
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)
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//Foote solo- never triggers with threshold over 1.0, threshold under mouse control
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(
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SynthDef(\fftod, {
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var source1, detect;
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source1= AudioIn.ar(1);
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detect= PV_HainsworthFoote.ar(FFT(LocalBuf(2048),source1), 0.0, 1.0, MouseX.kr(0.0,1.1), 0.02);
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Out.ar(0,Pan2.ar(source1,-1.0)+ Pan2.ar(SinOsc.ar(440,0,Decay.ar(0.1*detect,0.1)),1.0));
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}).play(s);
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)
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//compare to Amplitude UGen
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(
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SynthDef(\fftod, {
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var source1, detect;
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source1= AudioIn.ar(1);
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detect= (Amplitude.ar(source1)) > (MouseX.kr(0.0,1.1));
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Out.ar(0,Pan2.ar(source1,-1.0)+ Pan2.ar(SinOsc.ar(440,0,Decay.ar(0.1*detect,0.1)),1.0));
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}).play(s);
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)
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::
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]
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