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Merges the FFT scaling with the MDCT pre-rotate

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Jean-Marc Valin 2013-12-21 16:30:49 -05:00
parent 153def2884
commit c8f4e1608a
1 changed files with 14 additions and 7 deletions
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21
celt/mdct.c
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@ -182,20 +182,27 @@ void clt_mdct_forward(const mdct_lookup *l, kiss_fft_scalar *in, kiss_fft_scalar
for(i=0;i<N4;i++)
{
kiss_fft_cpx yc;
kiss_twiddle_scalar t0, t1;
kiss_fft_scalar re, im, yr, yi;
t0 = t[i<<shift];
t1 = t[(N4-i)<<shift];
#ifdef FIXED_POINT
t0 = MULT16_16_P15(t0, scale);
t1 = MULT16_16_P15(t1, scale);
#else
t0 *= st->scale;
t1 *= st->scale;
#endif
re = *yp++;
im = *yp++;
yr = -S_MUL(re,t[i<<shift]) - S_MUL(im,t[(N4-i)<<shift]);
yi = -S_MUL(im,t[i<<shift]) + S_MUL(re,t[(N4-i)<<shift]);
yr = -S_MUL(re,t0) - S_MUL(im,t1);
yi = -S_MUL(im,t0) + S_MUL(re,t1);
/* works because the cos is nearly one */
yc.r = yr + S_MUL(yi,sine);
yc.i = yi - S_MUL(yr,sine);
#ifdef FIXED_POINT
yc.r = SHR32(MULT16_32_Q15(scale, yc.r), scale_shift);
yc.i = SHR32(MULT16_32_Q15(scale, yc.i), scale_shift);
#else
yc.r *= st->scale;
yc.i *= st->scale;
yc.r = SHR32(yc.r, scale_shift);
yc.i = SHR32(yc.i, scale_shift);
#endif
f2[st->bitrev[i]] = yc;
}