ref: 9d420c58e939f6c972e0de5f41189ba214c26732
parent: 581fdba93690627d3a0faf61749596cf0284cd16
author: Jean-Marc Valin <[email protected]>
date: Fri May 28 13:26:27 EDT 2010
Viterbi-based RD optimization of the tf_res decisions
--- a/libcelt/celt.c
+++ b/libcelt/celt.c
@@ -546,9 +546,19 @@
int i, curr;
celt_word16 thresh1, thresh2;
VARDECL(celt_word16, metric);
+ VARDECL(celt_word16, cost0);
+ VARDECL(celt_word16, cost1);
+ VARDECL(int, path0);
+ VARDECL(int, path1);
+ /* FIXME: lambda should depend on the bit-rate */
+ celt_word16 lambda = 1;
SAVE_STACK;
ALLOC(metric, len, celt_word16);
+ ALLOC(cost0, len, celt_word16);
+ ALLOC(cost1, len, celt_word16);
+ ALLOC(path0, len, int);
+ ALLOC(path1, len, int);
for (i=0;i<len;i++)
metric[i] = bandLogE[i] - oldBandE[i];
if (C==2)
@@ -555,9 +565,6 @@
for (i=0;i<len;i++)
metric[i] = HALF32(metric[i] + (bandLogE[i+len] - oldBandE[i+len]));
- for (i=1;i<len-1;i++)
- metric[i] = (2*metric[i]+metric[i-1]+metric[i+1])/4;
-
if (isTransient)
{thresh1 = QCONST16(1.5f,DB_SHIFT);
@@ -566,20 +573,49 @@
thresh1 = QCONST16(1.5f,DB_SHIFT);
thresh2 = QCONST16(.8f,DB_SHIFT);
}
- curr = 0;
- for (i=0;i<len;i++)
+ cost0[0] = 0;
+ cost1[0] = lambda;
+ /* Viterbi forward pass */
+ for (i=1;i<len;i++)
{+ celt_word16 from0, from1;
+ cost0[i] = cost1[i] = 0;
if (metric[i]>thresh1)
- tf_res[i] = 1;
- else if (metric[i]>thresh2)
- tf_res[i] = curr;
+ cost0[i] = 1;
+ else if (metric[i]<thresh2)
+ cost1[i] = 1;
+
+ from0 = cost0[i-1];
+ from1 = cost1[i-1] + lambda;
+ if (from0 < from1)
+ {+ cost0[i] += from0;
+ path0[i]= 0;
+ } else {+ cost0[i] += from1;
+ path0[i]= 1;
+ }
+
+ from0 = cost0[i-1] + lambda;
+ from1 = cost1[i-1];
+ if (from0 < from1)
+ {+ cost1[i] += from0;
+ path1[i]= 0;
+ } else {+ cost1[i] += from1;
+ path1[i]= 1;
+ }
+ }
+ tf_res[len-1] = cost0[len-1] < cost1[len-1] ? 0 : 1;
+ /* Viterbi backward pass to check the decisions */
+ for (i=len-2;i>=0;i--)
+ {+ if (tf_res[i+1] == 1)
+ tf_res[i] = path1[i+1];
else
- tf_res[i] = 0;
+ tf_res[i] = path0[i+1];
}
- for (i=1;i<len-1;i++)
- if (tf_res[i] != tf_res[i-1] && tf_res[i] != tf_res[i+1])
- tf_res[i] = tf_res[i+1];
-
ec_enc_bit_prob(enc, tf_res[0], isTransient ? 64 : 16);
curr = tf_res[0];
for (i=1;i<len;i++)