static void fft_ref(FFTComplex *tabr, FFTComplex *tab, int nbits)
{
int n, i, j, k, n2;
double tmp_re, tmp_im, s, c;
FFTComplex *q;
n = 1 << nbits;
n2 = n >> 1;
for (i = 0; i < n; i++) {
tmp_re = 0;
tmp_im = 0;
q = tab;
for (j = 0; j < n; j++) {
k = (i * j) & (n - 1);
if (k >= n2) {
c = -exptab[k - n2].re;
s = -exptab[k - n2].im;
} else {
c = exptab[k].re;
s = exptab[k].im;
}
CMAC(tmp_re, tmp_im, c, s, q->re, q->im);
q++;
}
tabr[i].re = REF_SCALE(tmp_re, nbits);
tabr[i].im = REF_SCALE(tmp_im, nbits);
}
}
/* NOTE: no normalisation by 1 / N is done */
static void mdct_ref(FFTSample *output, FFTSample *input, int nbits)
{
int i, k, n = 1 << nbits;
/* do it by hand */
for (k = 0; k < n / 2; k++) {
double s = 0;
for (i = 0; i < n; i++) {
double a = (2 * M_PI * (2 * i + 1 + n / 2) * (2 * k + 1) / (4 * n));
s += input[i] * cos(a);
}
output[k] = REF_SCALE(s, nbits - 1);
}
}
static void imdct_ref(FFTSample *out, FFTSample *in, int nbits)
{
int i, k, n = 1 << nbits;
for (i = 0; i < n; i++) {
double sum = 0;
for (k = 0; k < n / 2; k++) {
int a = (2 * i + 1 + (n / 2)) * (2 * k + 1);
double f = cos(M_PI * a / (double) (2 * n));
sum += f * in[k];
}
out[i] = REF_SCALE(-sum, nbits - 2);
}
}