static void exp_rotation(celt_norm *X, int len, int dir, int stride, int K, int spread)
{
static const int SPREAD_FACTOR[3]= {15,10,5};
int i;
opus_val16 c, s;
opus_val16 gain, theta;
int stride2=0;
int factor;
if (2*K>=len || spread==SPREAD_NONE)
return;
factor = SPREAD_FACTOR[spread-1];
gain = celt_div((opus_val32)MULT16_16(Q15_ONE,len),(opus_val32)(len+factor*K));
theta = HALF16(MULT16_16_Q15(gain,gain));
c = celt_cos_norm(EXTEND32(theta));
s = celt_cos_norm(EXTEND32(SUB16(Q15ONE,theta))); /* sin(theta) */
if (len>=8*stride)
{
stride2 = 1;
/* This is just a simple (equivalent) way of computing sqrt(len/stride) with rounding.
It's basically incrementing long as (stride2+0.5)^2 < len/stride. */
while ((stride2*stride2+stride2)*stride + (stride>>2) < len)
stride2++;
}
static void exp_rotation(celt_norm *X, int len, int dir, int stride, int K)
{
int i, k, iter;
celt_word16 c, s;
celt_word16 gain, theta;
celt_norm *Xptr;
gain = celt_div((celt_word32)MULT16_16(Q15_ONE,len),(celt_word32)(3+len+6*K));
/* FIXME: Make that HALF16 instead of HALF32 */
theta = SUB16(Q15ONE, HALF32(MULT16_16_Q15(gain,gain)));
/*if (len==30)
{
for (i=0;i<len;i++)
X[i] = 0;
X[14] = 1;
}*/
c = celt_cos_norm(EXTEND32(theta));
s = dir*celt_cos_norm(EXTEND32(SUB16(Q15ONE,theta))); /* sin(theta) */
if (len > 8*stride)
stride *= len/(8*stride);
iter = 1;
for (k=0;k<iter;k++)
{
/* We could use MULT16_16_P15 instead of MULT16_16_Q15 for more accuracy,
but at this point, I really don't think it's necessary */
Xptr = X;
for (i=0;i<len-stride;i++)
{
celt_norm x1, x2;
x1 = Xptr[0];
x2 = Xptr[stride];
Xptr[stride] = MULT16_16_Q15(c,x2) + MULT16_16_Q15(s,x1);
*Xptr++ = MULT16_16_Q15(c,x1) - MULT16_16_Q15(s,x2);
}
Xptr = &X[len-2*stride-1];
for (i=len-2*stride-1;i>=0;i--)
{
celt_norm x1, x2;
x1 = Xptr[0];
x2 = Xptr[stride];
Xptr[stride] = MULT16_16_Q15(c,x2) + MULT16_16_Q15(s,x1);
*Xptr-- = MULT16_16_Q15(c,x1) - MULT16_16_Q15(s,x2);
}
}
/*if (len==30)
{
for (i=0;i<len;i++)
printf ("%f ", X[i]);
printf ("\n");
exit(0);
}*/
}
