annotate cq/CQParameters.h @ 149:2705ca19245c

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/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */
/*
    Constant-Q library
    Copyright (c) 2013-2014 Queen Mary, University of London

    Permission is hereby granted, free of charge, to any person
    obtaining a copy of this software and associated documentation
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    Except as contained in this notice, the names of the Centre for
    Digital Music; Queen Mary, University of London; and Chris Cannam
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*/

#ifndef CQ_PARAMETERS_H
#define CQ_PARAMETERS_H

/**
 * Common parameters for constructing Constant-Q implementation
 * objects (both forward and inverse transforms).
 */
class CQParameters
{
public:
    enum WindowType {
	SqrtBlackmanHarris,
	SqrtBlackman,
	SqrtHann,
	BlackmanHarris,
	Blackman,
	Hann,
    };

    /**
     * Construct a set of parameters with the given input signal
     * sample rate, frequency range, and number of bins per
     * octave. The remaining parameters will take their usual
     * defaults; if you want to change them, just assign the
     * respective data members after construction.
     */
    CQParameters(double _sampleRate, 
		 double _minFrequency, 
		 double _maxFrequency,
		 int _binsPerOctave) :
	sampleRate(_sampleRate),
	minFrequency(_minFrequency),
	maxFrequency(_maxFrequency),
	binsPerOctave(_binsPerOctave),
	q(1.0),                    // Q scaling factor
	atomHopFactor(0.25),       // hop size of shortest temporal atom
	threshold(0.0005),         // sparsity threshold for resulting kernel
	window(SqrtBlackmanHarris) // window shape
    { }

    /**
     * Sampling rate of input signal.
     */
    double sampleRate;

    /**
     * Minimum frequency desired to include in Constant-Q output. The
     * actual minimum will normally be calculated as a round number of
     * octaves below the maximum frequency, and may differ from this.
     */
    double minFrequency;

    /**
     * Maximum frequency to include in Constant-Q output.
     */
    double maxFrequency;

    /**
     * Number of output frequency bins per octave.
     */
    int binsPerOctave;

    /**
     * Spectral atom bandwidth scaling factor. q == 1 is optimal for
     * reconstruction, q < 1 increases redundancy (smearing) in the
     * frequency domain but improves time resolution.
     */
    double q;

    /**
     * Hop size between temporal atoms, where 1 == no overlap and
     * smaller values indicate overlapping atoms.
     */
    double atomHopFactor;

    /**
     * Sparsity threshold for Constant-Q kernel: values with magnitude
     * smaller than this are truncated to zero.
     */
    double threshold;

    /**
     * Window shape to use for the Constant-Q kernel atoms.
     */
    WindowType window;
};

#endif