for (i = 0; i < N; i++) { sum = 0; for (j = 0; j < N; j++) { sum += x[j] * cos(M_PI * (2 * j + 1) * i / (2 * N)); } x[i] = sum; } }
void fft(double *x, int N) { int i, j, k; double arg, c, s; digital media processing dsp algorithms using c pdf
void dct(double *x, int N) { int i, j; double sum; for (i = 0; i < N; i++)