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More simplifications to the Viterbi code

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This commit is contained in:
Jean-Marc Valin 2010-05-28 18:01:02 -04:00
parent 0ef39c9cc4
commit 8823261738
1 changed files with 16 additions and 17 deletions
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33
libcelt/celt.c
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@ -546,8 +546,8 @@ static void tf_encode(celt_word16 *bandLogE, celt_word16 *oldBandE, int len, int
int i, curr; int i, curr;
celt_word16 threshold; celt_word16 threshold;
VARDECL(celt_word16, metric); VARDECL(celt_word16, metric);
VARDECL(celt_word16, cost0); celt_word16 cost0;
VARDECL(celt_word16, cost1); celt_word16 cost1;
VARDECL(int, path0); VARDECL(int, path0);
VARDECL(int, path1); VARDECL(int, path1);
/* FIXME: lambda should depend on the bit-rate */ /* FIXME: lambda should depend on the bit-rate */
@ -555,8 +555,6 @@ static void tf_encode(celt_word16 *bandLogE, celt_word16 *oldBandE, int len, int
SAVE_STACK; SAVE_STACK;
ALLOC(metric, len, celt_word16); ALLOC(metric, len, celt_word16);
ALLOC(cost0, len, celt_word16);
ALLOC(cost1, len, celt_word16);
ALLOC(path0, len, int); ALLOC(path0, len, int);
ALLOC(path1, len, int); ALLOC(path1, len, int);
for (i=0;i<len;i++) for (i=0;i<len;i++)
@ -571,38 +569,39 @@ static void tf_encode(celt_word16 *bandLogE, celt_word16 *oldBandE, int len, int
} else { } else {
threshold = QCONST16(.5f,DB_SHIFT); threshold = QCONST16(.5f,DB_SHIFT);
} }
cost0[0] = 0; cost0 = 0;
cost1[0] = lambda; cost1 = lambda;
/* Viterbi forward pass */ /* Viterbi forward pass */
for (i=1;i<len;i++) for (i=1;i<len;i++)
{ {
celt_word16 curr0, curr1;
celt_word16 from0, from1; celt_word16 from0, from1;
cost1[i] = 0;
cost0[i] = metric[i]-threshold;
from0 = cost0[i-1]; from0 = cost0;
from1 = cost1[i-1] + lambda; from1 = cost1 + lambda;
if (from0 < from1) if (from0 < from1)
{ {
cost0[i] += from0; curr0 = from0;
path0[i]= 0; path0[i]= 0;
} else { } else {
cost0[i] += from1; curr0 = from1;
path0[i]= 1; path0[i]= 1;
} }
from0 = cost0[i-1] + lambda; from0 = cost0 + lambda;
from1 = cost1[i-1]; from1 = cost1;
if (from0 < from1) if (from0 < from1)
{ {
cost1[i] += from0; curr1 = from0;
path1[i]= 0; path1[i]= 0;
} else { } else {
cost1[i] += from1; curr1 = from1;
path1[i]= 1; path1[i]= 1;
} }
cost0 = curr0 + (metric[i]-threshold);
cost1 = curr1;
} }
tf_res[len-1] = cost0[len-1] < cost1[len-1] ? 0 : 1; tf_res[len-1] = cost0 < cost1 ? 0 : 1;
/* Viterbi backward pass to check the decisions */ /* Viterbi backward pass to check the decisions */
for (i=len-2;i>=0;i--) for (i=len-2;i>=0;i--)
{ {