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/* -*- 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_real(0)
{
m_private_real = new FFT(m_n);
}
FFTReal::~FFTReal()
{
delete (FFT *)m_private_real;
}
void
FFTReal::process(bool inverse,
const double *realIn,
double *realOut, double *imagOut)
{
((FFT *)m_private_real)->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;
}
}
}
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