ref: 3ccf3a5655601c5b5b883acaea3f07b8cb7d7321
parent: 8ddd7f400d124ab14697409cf286ad7b3f7039fb
author: Jean-Marc Valin <[email protected]>
date: Tue Apr 22 13:08:59 EDT 2008
Reverted to the old MDCT behaviour of only doing down-scaling in the FFT.
--- a/libcelt/mdct.c
+++ b/libcelt/mdct.c
@@ -86,13 +86,6 @@
celt_free(l->trig);
}
-/* Only divide by half if float. In fixed-point, it's included in the shift */
-#ifdef FIXED_POINT
-#define FL_HALF(x) (x)
-#else
-#define FL_HALF(x) (.5f*(x))
-#endif
-
void mdct_forward(const mdct_lookup *l, kiss_fft_scalar *in, kiss_fft_scalar * restrict out, const celt_word16_t *window, int overlap)
{int i;
@@ -116,8 +109,8 @@
for(i=0;i<(overlap>>2);i++)
{/* Real part arranged as -d-cR, Imag part arranged as -b+aR*/
- *yp++ = -FL_HALF(MULT16_32_Q16(*wp2, xp1[N2]) + MULT16_32_Q16(*wp1,*xp2));
- *yp++ = -FL_HALF(MULT16_32_Q16(*wp1, *xp1) - MULT16_32_Q16(*wp2, xp2[-N2]));
+ *yp++ = MULT16_32_Q15(*wp2, xp1[N2]) + MULT16_32_Q15(*wp1,*xp2);
+ *yp++ = MULT16_32_Q15(*wp1, *xp1) - MULT16_32_Q15(*wp2, xp2[-N2]);
xp1+=2;
xp2-=2;
wp1+=2;
@@ -128,8 +121,8 @@
for(;i<N4-(overlap>>2);i++)
{/* Real part arranged as a-bR, Imag part arranged as -c-dR */
- *yp++ = -HALF32(*xp2);
- *yp++ = -HALF32(*xp1);
+ *yp++ = *xp2;
+ *yp++ = *xp1;
xp1+=2;
xp2-=2;
}
@@ -136,8 +129,8 @@
for(;i<N4;i++)
{/* Real part arranged as a-bR, Imag part arranged as -c-dR */
- *yp++ = FL_HALF(MULT16_32_Q16(*wp1, xp1[-N2]) - MULT16_32_Q16(*wp2, *xp2));
- *yp++ = -FL_HALF(MULT16_32_Q16(*wp2, *xp1) + MULT16_32_Q16(*wp1, xp2[N2]));
+ *yp++ = -MULT16_32_Q15(*wp1, xp1[-N2]) + MULT16_32_Q15(*wp2, *xp2);
+ *yp++ = MULT16_32_Q15(*wp2, *xp1) + MULT16_32_Q15(*wp1, xp2[N2]);
xp1+=2;
xp2-=2;
wp1+=2;
@@ -153,16 +146,16 @@
kiss_fft_scalar re, im;
re = yp[0];
im = yp[1];
- *yp++ = S_MUL(re,t[0]) - S_MUL(im,t[N4]);
- *yp++ = S_MUL(im,t[0]) + S_MUL(re,t[N4]);
+ *yp++ = -S_MUL(re,t[0]) + S_MUL(im,t[N4]);
+ *yp++ = -S_MUL(im,t[0]) - S_MUL(re,t[N4]);
t++;
}
}
- /* N/4 complex FFT, which should normally down-scale by 4/N (but doesn't now) */
+ /* N/4 complex FFT, down-scales by 4/N */
cpx32_fft(l->kfft, out, f, N4);
- /* Post-rotate and apply the scaling if the FFT doesn't to it itself */
+ /* Post-rotate */
{/* Temp pointers to make it really clear to the compiler what we're doing */
const kiss_fft_scalar * restrict fp = f;
@@ -240,8 +233,8 @@
kiss_fft_scalar * restrict yp = f2;
for(i = 0; i < N4; i++)
{- *yp++ =-*fp1*2;
- *yp++ = *fp2*2;
+ *yp++ =-*fp1;
+ *yp++ = *fp2;
fp1 += 2;
fp2 -= 2;
}
--- a/libcelt/mdct.h
+++ b/libcelt/mdct.h
@@ -57,10 +57,11 @@
void mdct_init(mdct_lookup *l,int N);
void mdct_clear(mdct_lookup *l);
-/** Compute a forward MDCT and scale by 2/N */
+/** Compute a forward MDCT and scale by 4/N */
void mdct_forward(const mdct_lookup *l, kiss_fft_scalar *in, kiss_fft_scalar *out, const celt_word16_t *window, int overlap);
-/** Compute a backward MDCT (no scaling) and performs weighted overlap-add */
+/** Compute a backward MDCT (no scaling) and performs weighted overlap-add
+ (scales implicitly by 1/2) */
void mdct_backward(const mdct_lookup *l, kiss_fft_scalar *in, kiss_fft_scalar *out, const celt_word16_t * restrict window, int overlap);
#endif