annotate maths/MathUtilities.h @ 73:dcb555b90924

* Key detector: when returning key strengths, use the peak value of the
  three underlying chromagram correlations (from 36-bin chromagram)
  corresponding to each key, instead of the mean.
  Rationale: This is the same method as used when returning the key value,
  and it's nice to have the same results in both returned value and plot.
  The peak performed better than the sum with a simple test set of triads,
  so it seems reasonable to change the plot to match the key output rather
  than the other way around.

* FFT: kiss_fftr returns only the non-conjugate bins, synthesise the rest
  rather than leaving them (perhaps dangerously) undefined.  Fixes an
  uninitialised data error in chromagram that could cause garbage results
  from key detector.

* Constant Q: remove precalculated values again, I reckon they're not
  proving such a good tradeoff.

/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */

/*
    QM DSP Library

    Centre for Digital Music, Queen Mary, University of London.
    This file copyright 2005-2006 Christian Landone.
    All rights reserved.
*/

#ifndef MATHUTILITIES_H
#define MATHUTILITIES_H

#include <vector>

class MathUtilities  
{
public:	
    static double round( double x );

    static void	  getFrameMinMax( const double* data, unsigned int len,  double* min, double* max );

    static double mean( const double* src, unsigned int len );
    static double mean( const std::vector<double> &data,
                        unsigned int start, unsigned int count );
    static double sum( const double* src, unsigned int len );
    static double median( const double* src, unsigned int len );

    static double princarg( double ang );
    static double mod( double x, double y);

    static void	  getAlphaNorm(const double *data, unsigned int len, unsigned int alpha, double* ANorm);
    static double getAlphaNorm(const std::vector <double> &data, unsigned int alpha );

    static void   circShift( double* data, int length, int shift);

    static int	  getMax( double* data, unsigned int length, double* max = 0 );
    static int	  getMax( const std::vector<double> &data, double* max = 0 );
    static int    compareInt(const void * a, const void * b);

    enum NormaliseType {
        NormaliseNone,
        NormaliseUnitSum,
        NormaliseUnitMax
    };

    static void   normalise(double *data, int length,
                            NormaliseType n = NormaliseUnitMax);

    static void   normalise(std::vector<double> &data,
                            NormaliseType n = NormaliseUnitMax);

    // moving mean threshholding:
    static void adaptiveThreshold(std::vector<double> &data);

    static bool isPowerOfTwo(int x);
    static int nextPowerOfTwo(int x); // e.g. 1300 -> 2048, 2048 -> 2048
    static int previousPowerOfTwo(int x); // e.g. 1300 -> 1024, 2048 -> 2048
    static int nearestPowerOfTwo(int x); // e.g. 1300 -> 1024, 1700 -> 2048
};

#endif