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fixed-point: simplifying the arithmetic in alg_quant()

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This commit is contained in:
Jean-Marc Valin 2008-03-13 11:18:15 +11:00
parent 3ec78b173b
commit 19ae9fc944
3 changed files with 14 additions and 14 deletions
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20
libcelt/vq.c
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@ -218,24 +218,24 @@ void alg_quant(celt_norm_t *X, celt_mask_t *W, int N, int K, const celt_norm_t *
if (iy[m][j]*sign < 0)
continue;
spj = MULT16_16_P14(s, P[j]);
aspj = MULT16_16_P15(alpha, spj);
spj = MULT16_16_Q14(s, P[j]);
aspj = MULT16_16_Q15(alpha, spj);
/* Updating the sums of the new pulse(s) */
Rxy = xy[m] + MULT16_16(s,X[j]) - MULT16_16(MULT16_16_P15(alpha,spj),Rxp);
Rxy = xy[m] + MULT16_16(s,X[j]) - MULT16_16(MULT16_16_Q15(alpha,spj),Rxp);
Ryy = yy[m] + 2*MULT16_16(s,y[m][j]) + MULT16_16(s,s) +MULT16_16(aspj,MULT16_16_Q14(aspj,Rpp)) - 2*MULT16_32_Q14(aspj,yp[m]) - 2*MULT16_16(s,MULT16_16_Q14(aspj,P[j]));
Ryp = yp[m] + MULT16_16(spj, SUB16(QCONST16(1.f,14),MULT16_16_Q15(alpha,Rpp)));
/* Compute the gain such that ||p + g*y|| = 1 */
g = MULT32_32_Q31(
SHL32(celt_sqrt(MULT16_16(ROUND(Ryp,14),ROUND(Ryp,14)) + Ryy -
MULT16_16(ROUND(Ryy,14),Rpp))
- ROUND(Ryp,14), 14),
celt_rcp(ROUND(Ryy,14)));
g = MULT16_32_Q15(
celt_sqrt(MULT16_16(ROUND(Ryp,14),ROUND(Ryp,14)) + Ryy -
MULT16_16(ROUND(Ryy,14),Rpp))
- ROUND(Ryp,14),
celt_rcp(SHR32(Ryy,12)));
/* Knowing that gain, what's the error: (x-g*y)^2
(result is negated and we discard x^2 because it's constant) */
/*score = 2.f*g*Rxy - 1.f*g*g*Ryy*NORM_SCALING_1;*/
score = 2*MULT16_32_Q14(ROUND(Rxy,14),g) -
MULT16_32_Q14(EXTRACT16(MULT16_32_Q14(ROUND(Ryy,14),g)),g);
score = 2*MULT16_32_Q14(ROUND(Rxy,14),g)
- MULT16_32_Q14(EXTRACT16(MULT16_32_Q14(ROUND(Ryy,14),g)),g);
if (score>nbest[Lupdate-1]->score)
{