static void ki_work(
kiss_fft_cpx * Fout,
const kiss_fft_cpx * f,
size_t fstride,
int in_stride,
const celt_int16 * factors,
const kiss_fft_state *st,
int N,
int m2
)
{
const int p=*factors++; /* the radix */
const int m=*factors++; /* stage's fft length/p */
/*printf ("fft %d %d %d %d %d %d %d\n", p*m, m, p, s2, fstride*in_stride, N, m2);*/
if (m!=1)
ki_work( Fout , f, fstride*p, in_stride, factors,st, N*p, m);
/* Compensate for longer twiddles table (when sharing) */
if (st->shift>0)
fstride <<= st->shift;
switch (p) {
case 2: ki_bfly2(Fout,fstride,st,m, N, m2); break;
case 4: ki_bfly4(Fout,fstride,st,m, N, m2); break;
#ifndef RADIX_TWO_ONLY
case 3: ki_bfly3(Fout,fstride,st,m, N, m2); break;
case 5: ki_bfly5(Fout,fstride,st,m, N, m2); break;
#endif
}
}
void opus_ifft(const kiss_fft_state *st,const kiss_fft_cpx *fin,kiss_fft_cpx *fout)
{
int m2, m;
int p;
int L;
int fstride[MAXFACTORS];
int i;
int shift;
/* st->shift can be -1 */
shift = st->shift>0 ? st->shift : 0;
celt_assert2 (fin != fout, "In-place FFT not supported");
/* Bit-reverse the input */
for (i=0;i<st->nfft;i++)
fout[st->bitrev[i]] = fin[i];
fstride[0] = 1;
L=0;
do {
p = st->factors[2*L];
m = st->factors[2*L+1];
fstride[L+1] = fstride[L]*p;
L++;
} while(m!=1);
m = st->factors[2*L-1];
for (i=L-1;i>=0;i--)
{
if (i!=0)
m2 = st->factors[2*i-1];
else
m2 = 1;
switch (st->factors[2*i])
{
case 2:
ki_bfly2(fout,fstride[i]<<shift,st,m, fstride[i], m2);
break;
case 4:
ki_bfly4(fout,fstride[i]<<shift,st,m, fstride[i], m2);
break;
#ifndef RADIX_TWO_ONLY
case 3:
ki_bfly3(fout,fstride[i]<<shift,st,m, fstride[i], m2);
break;
case 5:
ki_bfly5(fout,fstride[i]<<shift,st,m, fstride[i], m2);
break;
#endif
}
m = m2;
}
}
