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Further simplifications to the forward mdct

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This commit is contained in:
Jean-Marc Valin 2008-04-22 09:49:22 +10:00
parent 41880805ab
commit ef0d5f15c7
5 changed files with 28 additions and 32 deletions
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40
libcelt/mdct.c
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@ -111,8 +111,11 @@ void mdct_forward(const mdct_lookup *l, kiss_fft_scalar *in, kiss_fft_scalar * r
{
kiss_fft_scalar re, im;
/* Real part arranged as -d-cR, Imag part arranged as -b+aR*/
re = -HALF32(MULT16_32_Q15(*wp2, xp1[N2]) + MULT16_32_Q15(*wp1,*xp2));
im = -HALF32(MULT16_32_Q15(*wp1, *xp1) - MULT16_32_Q15(*wp2, xp2[-N2]));
re = -(MULT16_32_Q16(*wp2, xp1[N2]) + MULT16_32_Q16(*wp1,*xp2));
im = -(MULT16_32_Q16(*wp1, *xp1) - MULT16_32_Q16(*wp2, xp2[-N2]));
#ifndef FIXED_POINT
re *= .5; im *= .5;
#endif
xp1+=2;
xp2-=2;
wp1+=2;
@ -123,10 +126,12 @@ void mdct_forward(const mdct_lookup *l, kiss_fft_scalar *in, kiss_fft_scalar * r
*yp++ = S_MUL(im,t[0]) + S_MUL(re,t[N4]);
t++;
}
for(;i<N/8;i++)
wp1 = window;
wp2 = window+overlap-1;
for(;i<N4-overlap/4;i++)
{
kiss_fft_scalar re, im;
/* Real part arranged as -d-cR, Imag part arranged as -b+aR*/
/* Real part arranged as a-bR, Imag part arranged as -c-dR */
re = -HALF32(*xp2);
im = -HALF32(*xp1);
xp1+=2;
@ -135,30 +140,17 @@ void mdct_forward(const mdct_lookup *l, kiss_fft_scalar *in, kiss_fft_scalar * r
(MIXED_PRECISION only) */
*yp++ = S_MUL(re,t[0]) - S_MUL(im,t[N4]);
*yp++ = S_MUL(im,t[0]) + S_MUL(re,t[N4]);
t++;
}
wp1 = window;
wp2 = window+overlap-1;
for(;i<N4-overlap/4;i++)
{
kiss_fft_scalar re, im;
/* Real part arranged as a-bR, Imag part arranged as -c-dR */
re = HALF32(-*xp2);
im = -HALF32(*xp1);
xp1+=2;
xp2-=2;
/* We could remove the HALF32 above and just use MULT16_32_Q16 below
(MIXED_PRECISION only) */
*yp++ = S_MUL(re,t[0]) - S_MUL(im,t[N4]);
*yp++ = S_MUL(im,t[0]) + S_MUL(re,t[N4]);
t++;
t++;
}
for(;i<N4;i++)
{
kiss_fft_scalar re, im;
/* Real part arranged as a-bR, Imag part arranged as -c-dR */
re = HALF32(MULT16_32_Q15(*wp1, xp1[-N2]) - MULT16_32_Q15(*wp2, *xp2));
im = -HALF32(MULT16_32_Q15(*wp2, *xp1) + MULT16_32_Q15(*wp1, xp2[N2]));
re = (MULT16_32_Q16(*wp1, xp1[-N2]) - MULT16_32_Q16(*wp2, *xp2));
im = -(MULT16_32_Q16(*wp2, *xp1) + MULT16_32_Q16(*wp1, xp2[N2]));
#ifndef FIXED_POINT
re *= .5; im *= .5;
#endif
xp1+=2;
xp2-=2;
wp1+=2;
@ -189,7 +181,7 @@ void mdct_forward(const mdct_lookup *l, kiss_fft_scalar *in, kiss_fft_scalar * r
fp += 2;
yp1 += 2;
yp2 -= 2;
t++;
t++;
}
}
RESTORE_STACK;