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optimisation: intra_prediction() uses a 16-bit numerator for the search

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This commit is contained in:
Jean-Marc Valin 2008-04-16 10:29:01 +10:00
parent eac9970c94
commit 0a864645f9
1 changed files with 4 additions and 4 deletions
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8
libcelt/vq.c
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@ -273,7 +273,7 @@ void intra_prediction(celt_norm_t *x, celt_mask_t *W, int N, int K, celt_norm_t
{ {
int i,j,c; int i,j,c;
int best=0; int best=0;
celt_word32_t best_num=-SHR32(VERY_LARGE32,4); celt_word16_t best_num=-VERY_LARGE16;
celt_word16_t best_den=0; celt_word16_t best_den=0;
celt_word16_t s = 1; celt_word16_t s = 1;
int sign; int sign;
@ -296,7 +296,7 @@ void intra_prediction(celt_norm_t *x, celt_mask_t *W, int N, int K, celt_norm_t
for (i=0;i<max_pos;i++) for (i=0;i<max_pos;i++)
{ {
celt_word32_t xy=0, yy=0; celt_word32_t xy=0, yy=0;
celt_word32_t num; celt_word16_t num;
celt_word16_t den; celt_word16_t den;
const celt_word16_t * restrict xp = Xr; const celt_word16_t * restrict xp = Xr;
const celt_word16_t * restrict yp = Y+B*i; const celt_word16_t * restrict yp = Y+B*i;
@ -310,11 +310,11 @@ void intra_prediction(celt_norm_t *x, celt_mask_t *W, int N, int K, celt_norm_t
yp++; yp++;
} while (++j<B*N); /* Promises we loop at least once */ } while (++j<B*N); /* Promises we loop at least once */
/* Using xy^2/yy as the score but without having to do the division */ /* Using xy^2/yy as the score but without having to do the division */
num = MULT16_16(ROUND16(xy,14),ROUND16(xy,14)); num = MULT16_16_Q15(ROUND16(xy,14),ROUND16(xy,14));
den = ROUND16(yy,14); den = ROUND16(yy,14);
/* If you're really desperate for speed, just use xy as the score */ /* If you're really desperate for speed, just use xy as the score */
/* OPT: Make sure to use a conditional move here */ /* OPT: Make sure to use a conditional move here */
if (MULT16_32_Q15(best_den, num) > MULT16_32_Q15(den, best_num)) if (MULT16_16(best_den, num) > MULT16_16(den, best_num))
{ {
best_num = num; best_num = num;
best_den = den; best_den = den;