HelpSource/Classes/PV_HainsworthFoote.schelp

   1 class:: PV_HainsworthFoote
   2 summary:: FFT onset detector.
   3 related:: Classes/PV_JensenAndersen
   4 categories::  UGens>FFT
   5
   6
   7 Description::
   8
   9 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. ::
  10 See especially p128. The Hainsworth metric is a modification of the Kullback Liebler
  11 distance.
  12
  13
  14 The onset detector has general ability to spot spectral change, so may
  15 have some ability to track chord changes  aside from obvious transient
  16 jolts, but there's no guarantee it won't be confused by frequency
  17 modulation artifacts.
  18
  19
  20 Hainsworth metric on it's own gives good results but Foote might be
  21 useful in some situations: experimental.
  22
  23
  24 classmethods::
  25 private:: categories
  26
  27 method::ar
  28
  29 argument::buffer
  30
  31 FFT buffer.
  32
  33
  34 argument::proph
  35
  36 What strength of detection signal from Hainsworth metric to use.
  37
  38
  39 argument::propf
  40
  41 What strength of detection signal from Foote metric to use. The
  42 Foote metric is normalised to (0..1).
  43
  44
  45 argument::threshold
  46
  47 Threshold hold level for allowing a detection.
  48
  49
  50 argument::waittime
  51
  52 If triggered, minimum wait until a further frame can cause
  53 another spot (useful to stop multiple detects on heavy signals).
  54
  55
  56 Examples::
  57
  58 code::
  59
  60 //just Hainsworth metric with low threshold
  61 (
  62 b=Buffer.alloc(s,2048,1);
  63
  64 SynthDef(\fftod,
  65 {
  66  var source1, detect;
  67
  68         source1= AudioIn.ar(1);
  69
  70         detect= PV_HainsworthFoote.ar(FFT(b.bufnum,source1), 1.0, 0.0);
  71
  72         Out.ar(0,SinOsc.ar([440,445],0,Decay.ar(0.1*detect,0.1)));
  73 }).play(s);
  74 )
  75
  76
  77 //spot note transitions
  78 (
  79 b=Buffer.alloc(s,2048,1);
  80
  81 SynthDef(\fftod,
  82 {
  83  var source1, detect;
  84
  85         source1= LFSaw.ar(LFNoise0.kr(1,90,400),0,0.5);
  86
  87         detect= PV_HainsworthFoote.ar(FFT(b.bufnum,source1), 1.0, 0.0, 0.9, 0.5);
  88
  89         Out.ar(0,Pan2.ar(source1,-1.0)+ Pan2.ar(SinOsc.ar(440,0,Decay.ar(0.1*detect,0.1)),1.0));
  90 }).play(s);
  91 )
  92
  93
  94
  95 //Foote solo- never triggers with threshold over 1.0, threshold under mouse control
  96 (
  97 b=Buffer.alloc(s,2048,1);
  98
  99 SynthDef(\fftod,
 100 {
 101  var source1, detect;
 102
 103         source1= AudioIn.ar(1);
 104
 105         detect= PV_HainsworthFoote.ar(FFT(b.bufnum,source1), 0.0, 1.0, MouseX.kr(0.0,1.1), 0.02);
 106
 107         Out.ar(0,Pan2.ar(source1,-1.0)+ Pan2.ar(SinOsc.ar(440,0,Decay.ar(0.1*detect,0.1)),1.0));
 108 }).play(s);
 109 )
 110
 111
 112 //compare to Amplitude UGen
 113 (
 114 b=Buffer.alloc(s,2048,1);
 115
 116 SynthDef(\fftod,
 117 {
 118  var source1, detect;
 119
 120         source1= AudioIn.ar(1);
 121
 122         detect= (Amplitude.ar(source1)) > (MouseX.kr(0.0,1.1));
 123
 124         Out.ar(0,Pan2.ar(source1,-1.0)+ Pan2.ar(SinOsc.ar(440,0,Decay.ar(0.1*detect,0.1)),1.0));
 125 }).play(s);
 126 )
 127
 128 ::
 129