void FFT::fft(int n, int logn, Complex *z) {
switch (logn) {
case 2:
fft4(z);
break;
case 3:
fft8(z);
break;
case 4:
fft16(z);
break;
default:
fft((n / 2), logn - 1, z);
fft((n / 4), logn - 2, z + (n / 4) * 2);
fft((n / 4), logn - 2, z + (n / 4) * 3);
assert(_cosTables[logn - 4]);
if (n > 1024)
pass_big(z, _cosTables[logn - 4]->getTable(), (n / 4) / 2);
else
pass(z, _cosTables[logn - 4]->getTable(), (n / 4) / 2);
}
}
/*******************************************************************************
Functionname: sinMod
*******************************************************************************
Description: Performs sine modulation.
Return: none
*******************************************************************************/
static void
sinMod (float *subband, HANDLE_SBR_QMF_FILTER_BANK qmfBank)
{
int i;
float wre, wim;
float re1, im1, re2, im2;
/* subband[2 * i]
subband[32 - 2 * i]
qmfBank->sin_twiddle[i]
qmfBank->cos_twiddle[i]
qmfBank->sin_twiddle[15 - i]
qmfBank->cos_twiddle[15 - i]
*/
for (i = 0; i < 8; i++) {
re1 = subband[2 * i];
im2 = subband[2 * i + 1];
re2 = subband[30 - 2 * i];
im1 = subband[31 - 2 * i];
wre = qmfBank->sin_twiddle[i];
wim = qmfBank->cos_twiddle[i];
subband[2 * i + 1] = im1 * wim + re1 * wre;
subband[2 * i] = im1 * wre - re1 * wim;
wre = qmfBank->sin_twiddle[15 - i];
wim = qmfBank->cos_twiddle[15 - i];
subband[31 - 2 * i] = im2 * wim + re2 * wre;
subband[30 - 2 * i] = im2 * wre - re2 * wim;
}
fft16(subband);
/* subband[2 * i],
subband[32 - 2 * i],
qmfBank->alt_sin_twiddle[i],
qmfBank->sin_twiddle[15 - i]
*/
wim = qmfBank->alt_sin_twiddle[0];
wre = qmfBank->alt_sin_twiddle[16];
for (i = 0; i < 8; i++) {
re1 = subband[2 * i];
im1 = subband[2 * i + 1];
re2 = subband[30 - 2 * i];
im2 = subband[31 - 2 * i];
subband[31 - 2 * i] = -(re1 * wre + im1 * wim);
subband[2 * i] = -(re1 * wim - im1 * wre);
wim = qmfBank->alt_sin_twiddle[i + 1];
wre = qmfBank->alt_sin_twiddle[15 - i];
subband[2 * i + 1] = -(re2 * wim + im2 * wre);
subband[30 - 2 * i] = -(re2 * wre - im2 * wim);
}
}
