gstfft
#include <gst/fft/gstfft.h>
gint gst_fft_next_fast_length (gint n);
gint n
GST_FFT_WINDOW_RECTANGULAR
GST_FFT_WINDOW_HAMMING
GST_FFT_WINDOW_HANN
GST_FFT_WINDOW_BARTLETT
GST_FFT_WINDOW_BLACKMAN