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;
}
}
}
bool FastFourierTransform::FFT(int NumSamples,bool InverseTransform,double *RealIn, double *ImagIn, double *RealOut, double *ImagOut){
int NumBits; /* Number of bits needed to store indices */
int i, j, k, n;
int BlockSize, BlockEnd;
double angle_numerator = 2.0 * PI;
double tr, ti; /* temp real, temp imaginary */
if ( !isPowerOfTwo(NumSamples) ) {
fprintf(stderr, "%d is not a power of two\n", NumSamples);
return false;
}
if (!gFFTBitTable)
initFFT();
if (InverseTransform)
angle_numerator = -angle_numerator;
NumBits = numberOfBitsNeeded(NumSamples);
//Simultaneously data copy and bit-reversal ordering into outputs...
for(i = 0; i < NumSamples; i++) {
j = fastReverseBits(i, NumBits);
RealOut[j] = RealIn[i];
ImagOut[j] = (ImagIn == NULL) ? 0.0 : ImagIn[i];
}
//Do the FFT
BlockEnd = 1;
for (BlockSize = 2; BlockSize <= NumSamples; 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 ar0, ar1, ar2, ai0, ai1, ai2;
for (i = 0; i < NumSamples; i += BlockSize) {
ar2 = cm2;
ar1 = cm1;
ai2 = sm2;
ai1 = sm1;
for (j = i, n = 0; n < BlockEnd; j++, n++) {
ar0 = w * ar1 - ar2;
ar2 = ar1;
ar1 = ar0;
ai0 = w * ai1 - ai2;
ai2 = ai1;
ai1 = ai0;
k = j + BlockEnd;
tr = ar0 * RealOut[k] - ai0 * ImagOut[k];
ti = ar0 * ImagOut[k] + ai0 * RealOut[k];
RealOut[k] = RealOut[j] - tr;
ImagOut[k] = ImagOut[j] - ti;
RealOut[j] += tr;
ImagOut[j] += ti;
}
}
BlockEnd = BlockSize;
}
//Need to normalize the results if we are computing the inverse transform
if( InverseTransform ){
double denom = (double) NumSamples;
for(i = 0; i < NumSamples; i++) {
RealOut[i] /= denom;
ImagOut[i] /= denom;
}
}
return true;
}
