static void fft_ref_init(int nbits, int inverse) { int i, n = 1 << nbits; exptab = av_malloc((n / 2) * sizeof(*exptab)); for (i = 0; i < (n/2); i++) { double alpha = 2 * M_PI * (float)i / (float)n; double c1 = cos(alpha), s1 = sin(alpha); if (!inverse) s1 = -s1; exptab[i].re = c1; exptab[i].im = s1; } }