annotate dsp/transforms/FFT.cpp @ 96:88f3cfcff55f

A threshold (delta) is added in the peak picking parameters structure (PPickParams). It is used as an offset when computing the smoothed detection function. A constructor for the structure PPickParams is also added to set the parameters to 0 when a structure instance is created. Hence programmes using the peak picking parameter structure and which do not set the delta parameter (e.g. QM Vamp note onset detector) won't be affected by the modifications.

Functions modified:
- dsp/onsets/PeakPicking.cpp
- dsp/onsets/PeakPicking.h
- dsp/signalconditioning/DFProcess.cpp
- dsp/signalconditioning/DFProcess.h

/* -*- 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 is based on Don Cross's public domain FFT implementation.
*/

#include "FFT.h"

#include "maths/MathUtilities.h"

#include <cmath>

#include <iostream>

FFT::FFT(unsigned int n) :
    m_n(n),
    m_private(0)
{
    if( !MathUtilities::isPowerOfTwo(m_n) )
    {
        std::cerr << "ERROR: FFT: Non-power-of-two FFT size "
                  << m_n << " not supported in this implementation"
                  << std::endl;
	return;
    }
}

FFT::~FFT()
{

}

FFTReal::FFTReal(unsigned int n) :
    m_n(n),
    m_private(0)
{
    m_private = new FFT(m_n);
}

FFTReal::~FFTReal()
{
    delete (FFT *)m_private;
}

void
FFTReal::process(bool inverse,
                 const double *realIn,
                 double *realOut, double *imagOut)
{
    ((FFT *)m_private)->process(inverse, realIn, 0, realOut, imagOut);
}

static unsigned int numberOfBitsNeeded(unsigned int p_nSamples)
{	
    int i;

    if( p_nSamples < 2 )
    {
	return 0;
    }

    for ( i=0; ; i++ )
    {
	if( p_nSamples & (1 << i) ) return i;
    }
}

static unsigned int reverseBits(unsigned int p_nIndex, unsigned int p_nBits)
{
    unsigned int i, rev;

    for(i=rev=0; i < p_nBits; i++)
    {
	rev = (rev << 1) | (p_nIndex & 1);
	p_nIndex >>= 1;
    }

    return rev;
}

void
FFT::process(bool p_bInverseTransform,
             const double *p_lpRealIn, const double *p_lpImagIn,
             double *p_lpRealOut, double *p_lpImagOut)
{
    if (!p_lpRealIn || !p_lpRealOut || !p_lpImagOut) return;

//    std::cerr << "FFT::process(" << m_n << "," << p_bInverseTransform << ")" << std::endl;

    unsigned int NumBits;
    unsigned int i, j, k, n;
    unsigned int BlockSize, BlockEnd;

    double angle_numerator = 2.0 * M_PI;
    double tr, ti;

    if( !MathUtilities::isPowerOfTwo(m_n) )
    {
        std::cerr << "ERROR: FFT::process: Non-power-of-two FFT size "
                  << m_n << " not supported in this implementation"
                  << std::endl;
	return;
    }

    if( p_bInverseTransform ) angle_numerator = -angle_numerator;

    NumBits = numberOfBitsNeeded ( m_n );


    for( i=0; i < m_n; i++ )
    {
	j = reverseBits ( i, NumBits );
	p_lpRealOut[j] = p_lpRealIn[i];
	p_lpImagOut[j] = (p_lpImagIn == 0) ? 0.0 : p_lpImagIn[i];
    }


    BlockEnd = 1;
    for( BlockSize = 2; BlockSize <= m_n; BlockSize <<= 1 )
    {
	double delta_angle = angle_numerator / (double)BlockSize;
	double sm2 = -sin ( -2 * delta_angle );
	double sm1 = -sin ( -delta_angle );
	double cm2 = cos ( -2 * delta_angle );
	double cm1 = cos ( -delta_angle );
	double w = 2 * cm1;
	double ar[3], ai[3];

	for( i=0; i < m_n; i += BlockSize )
	{

	    ar[2] = cm2;
	    ar[1] = cm1;

	    ai[2] = sm2;
	    ai[1] = sm1;

	    for ( j=i, n=0; n < BlockEnd; j++, n++ )
	    {

		ar[0] = w*ar[1] - ar[2];
		ar[2] = ar[1];
		ar[1] = ar[0];

		ai[0] = w*ai[1] - ai[2];
		ai[2] = ai[1];
		ai[1] = ai[0];

		k = j + BlockEnd;
		tr = ar[0]*p_lpRealOut[k] - ai[0]*p_lpImagOut[k];
		ti = ar[0]*p_lpImagOut[k] + ai[0]*p_lpRealOut[k];

		p_lpRealOut[k] = p_lpRealOut[j] - tr;
		p_lpImagOut[k] = p_lpImagOut[j] - ti;

		p_lpRealOut[j] += tr;
		p_lpImagOut[j] += ti;

	    }
	}

	BlockEnd = BlockSize;

    }


    if( p_bInverseTransform )
    {
	double denom = (double)m_n;

	for ( i=0; i < m_n; i++ )
	{
	    p_lpRealOut[i] /= denom;
	    p_lpImagOut[i] /= denom;
	}
    }
}