For the first case (2D real-to-complex FFT) you need to use the API in tools/kiss_fftndr.h
:
kiss_fftndr_cfg kiss_fftndr_alloc(const int *dims,int ndims,int inverse_fft,void*mem,size_t*lenmem);
void kiss_fftndr(
kiss_fftndr_cfg cfg,
const kiss_fft_scalar *timedata,
kiss_fft_cpx *freqdata);
void kiss_fftndri(
kiss_fftndr_cfg cfg,
const kiss_fft_cpx *freqdata,
kiss_fft_scalar *timedata);
For the second case (1D complex-to-real FFT) you need to use the API in tools/kiss_fftr.h
:
kiss_fftr_cfg kiss_fftr_alloc(int nfft,int inverse_fft,void * mem, size_t * lenmem);
void kiss_fftr(kiss_fftr_cfg cfg,const kiss_fft_scalar *timedata,kiss_fft_cpx *freqdata);
void kiss_fftri(kiss_fftr_cfg cfg,const kiss_fft_cpx *freqdata,kiss_fft_scalar *timedata);