109 lines
3.4 KiB
C++
109 lines
3.4 KiB
C++
#ifndef Helmholtz_H
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#define Helmholtz_H
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/***********************************************************************
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Class Helmholtz implements a period-length detector using Philip McLeod's
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Specially Normalized AutoCorrelation function (SNAC).
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Function iosamples() takes a pointer to a buffer with n signal input samples
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and a pointer to a buffer where n output samples are stored,
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representing the SNAC function.
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Via function setframesize(), analysis frame size can be set to
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128, 256, 512, 1024 or 2048 samples. Default is 1024.
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With setoverlap(), analysis frames can be set to overlap each other
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with factor 1, 2, 4 or 8. Default is 1.
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Function setbias() sets a bias which favours small lags over large lags in
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the period detection, thereby avoiding low-octave jumps. Default is 0.2
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Function setminRMS() is used as a sensitivity setting. Default is RMS 0.003.
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With function getperiod(), the last detected period length is returned
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as number of samples with a possible fraction (floating point format).
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Function getfidelity() returns a value between 0. and 1. indicating
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to which extent the input signal is periodic. A fidelity of ~0.95 can
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be considered to indicate a periodic signal.
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Class Helmholtz needs mayer_realfft() and mayer_realifft() or similar
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fft functions. Note that Ron Mayer's functions for real fft have a
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peculiar organisation of imaginary coefficients (reversed order, sign flipped).
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Class Helmholtz uses t_float for float or double. Depending on the context
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where the class is used, you may need to define t_float. If used with
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PD or MaxMsp, it is already defined.
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***********************************************************************
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Licensed under three-clause BSD license.
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Katja Vetter, Feb 2012.
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***********************************************************************/
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/* This section includes the Pure Data API header. If you build Helmholtz
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against another DSP framework, you need to define t_float, and you need to
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include Ron Mayer's fft or similar functionality. */
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#include "mayer_fft.h"
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#define REALFFT mayer_realfft
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#define REALIFFT mayer_realifft
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/***********************************************************************/
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#define DEFFRAMESIZE 1024 // default analysis framesize
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#define DEFOVERLAP 1 // default overlap
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#define DEFBIAS 0.2 // default bias
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#define DEFMINRMS 0.003 // default minimum RMS
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#define SEEK 0.85 // seek-length as ratio of framesize
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#define t_float float
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class Helmholtz
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{
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public:
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Helmholtz(int periodarg = DEFFRAMESIZE, int overlaparg = DEFOVERLAP, t_float biasarg = DEFBIAS);
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~Helmholtz();
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void iosamples(const t_float* in, t_float* out, int size);
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void setframesize(int frame);
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void setoverlap(int lap);
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void setbias(t_float bias);
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void setminRMS(t_float rms);
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t_float getperiod() const;
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t_float getfidelity() const;
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private:
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// procedures
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void analyzeframe();
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void autocorrelation();
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void normalize();
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void pickpeak();
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void periodandfidelity();
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// functions
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t_float interpolate3max(t_float* buf, int peakindex);
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t_float interpolate3phase(t_float* buf, int peakindex);
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// buffers
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t_float inputbuf[2048];
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t_float inputbuf2[2048];
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t_float processbuf[4096];
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// state variables
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int timeindex;
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int framesize;
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int overlap;
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int periodindex;
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t_float periodlength;
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t_float fidelity;
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t_float biasfactor;
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t_float minrms;
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};
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#endif // #ifndef Helmholtz_H
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