/*
* InverseRealFFT
*
* This function computes the inverse of RealFFT, above.
* The RealIn and ImagIn is assumed to be conjugate-symmetric
* and as a result the output is purely real.
* Only the first half of RealIn and ImagIn are used due to this
* symmetry assumption.
*/
void InverseRealFFT(int NumSamples, float *RealIn, float *ImagIn, float *RealOut)
{
// Remap to RealFFTf() function
int i;
HFFT hFFT = GetFFT(NumSamples);
float *pFFT = new float[NumSamples];
// Copy the data into the processing buffer
for(i=0; i<(NumSamples/2); i++)
pFFT[2*i ] = RealIn[i];
if(ImagIn == NULL) {
for(i=0; i<(NumSamples/2); i++)
pFFT[2*i+1] = 0;
} else {
for(i=0; i<(NumSamples/2); i++)
pFFT[2*i+1] = ImagIn[i];
}
// Put the fs/2 component in the imaginary part of the DC bin
pFFT[1] = RealIn[i];
// Perform the FFT
InverseRealFFTf(pFFT, hFFT);
// Copy the data to the (purely real) output buffer
ReorderToTime(hFFT, pFFT, RealOut);
delete [] pFFT;
ReleaseFFT(hFFT);
}
/*
* InverseRealFFT
*
* This function computes the inverse of RealFFT, above.
* The RealIn and ImagIn is assumed to be conjugate-symmetric
* and as a result the output is purely real.
* Only the first half of RealIn and ImagIn are used due to this
* symmetry assumption.
*
* This is merely a wrapper of InverseRealFFTf() from RealFFTf.h.
*/
void InverseRealFFT(size_t NumSamples, const float *RealIn, const float *ImagIn,
float *RealOut)
{
auto hFFT = GetFFT(NumSamples);
Floats pFFT{ NumSamples };
// Copy the data into the processing buffer
for (size_t i = 0; i < (NumSamples / 2); i++)
pFFT[2*i ] = RealIn[i];
if(ImagIn == NULL) {
for (size_t i = 0; i < (NumSamples / 2); i++)
pFFT[2*i+1] = 0;
} else {
for (size_t i = 0; i < (NumSamples / 2); i++)
pFFT[2*i+1] = ImagIn[i];
}
// Put the fs/2 component in the imaginary part of the DC bin
pFFT[1] = RealIn[NumSamples / 2];
// Perform the FFT
InverseRealFFTf(pFFT.get(), hFFT.get());
// Copy the data to the (purely real) output buffer
ReorderToTime(hFFT.get(), pFFT.get(), RealOut);
}
