Balancing coef-tree to reduce bool decodes

This patch changes the coefficient tree to move the EOB to below
the ZERO node in order to save number of bool decodes.

The advantages of moving EOB one step down as opposed to two steps down
in the other parallel patch are: 1. The coef modeling based on
the One-node becomes independent of the tree structure above it, and
2. Fewer conext/counter increases are needed.

The drawback is that the potential savings in bool decodes will be
less, but assuming that 0s are much more predominant than 1's the
potential savings is still likely to be substantial.

Results on derf300: -0.237%

Change-Id: Ie784be13dc98291306b338e8228703a4c2ea2242

1 files changed, 36 insertions, 2 deletions

diff --git a/vp9/encoder/vp9_encodemb.c b/vp9/encoder/vp9_encodemb.c
index 755ff21bf..98ea98031 100644
--- a/vp9/encoder/vp9_encodemb.c
+++ b/vp9/encoder/vp9_encodemb.c
@@ -215,10 +215,21 @@ static void optimize_b(VP9_COMMON *const cm, MACROBLOCK *mb,
         band = get_coef_band(band_translate, i + 1);
         pt = trellis_get_coeff_context(scan, nb, i, t0, token_cache,
                                        pad, default_eob);
+#if CONFIG_BALANCED_COEFTREE
         rate0 +=
-          mb->token_costs[tx_size][type][ref][band][pt][tokens[next][0].token];
+          mb->token_costs_noskip[tx_size][type][ref][band][pt]
+                                [tokens[next][0].token];
         rate1 +=
-          mb->token_costs[tx_size][type][ref][band][pt][tokens[next][1].token];
+          mb->token_costs_noskip[tx_size][type][ref][band][pt]
+                                [tokens[next][1].token];
+#else
+        rate0 +=
+          mb->token_costs[tx_size][type][ref][band][pt]
+                         [tokens[next][0].token];
+        rate1 +=
+          mb->token_costs[tx_size][type][ref][band][pt]
+                         [tokens[next][1].token];
+#endif
       }
       UPDATE_RD_COST();
       /* And pick the best. */
@@ -266,14 +277,32 @@ static void optimize_b(VP9_COMMON *const cm, MACROBLOCK *mb,
         if (t0 != DCT_EOB_TOKEN) {
           pt = trellis_get_coeff_context(scan, nb, i, t0, token_cache,
                                          pad, default_eob);
+#if CONFIG_BALANCED_COEFTREE
+          if (!x)
+            rate0 += mb->token_costs[tx_size][type][ref][band][pt][
+                tokens[next][0].token];
+          else
+            rate0 += mb->token_costs_noskip[tx_size][type][ref][band][pt][
+                tokens[next][0].token];
+#else
           rate0 += mb->token_costs[tx_size][type][ref][band][pt][
               tokens[next][0].token];
+#endif
         }
         if (t1 != DCT_EOB_TOKEN) {
           pt = trellis_get_coeff_context(scan, nb, i, t1, token_cache,
                                          pad, default_eob);
+#if CONFIG_BALANCED_COEFTREE
+          if (!x)
+            rate1 += mb->token_costs[tx_size][type][ref][band][pt][
+                tokens[next][1].token];
+          else
+            rate1 += mb->token_costs_noskip[tx_size][type][ref][band][pt][
+                tokens[next][1].token];
+#else
           rate1 += mb->token_costs[tx_size][type][ref][band][pt][
               tokens[next][1].token];
+#endif
         }
       }
 
@@ -326,8 +355,13 @@ static void optimize_b(VP9_COMMON *const cm, MACROBLOCK *mb,
   error1 = tokens[next][1].error;
   t0 = tokens[next][0].token;
   t1 = tokens[next][1].token;
+#if CONFIG_BALANCED_COEFTREE
+  rate0 += mb->token_costs_noskip[tx_size][type][ref][band][pt][t0];
+  rate1 += mb->token_costs_noskip[tx_size][type][ref][band][pt][t1];
+#else
   rate0 += mb->token_costs[tx_size][type][ref][band][pt][t0];
   rate1 += mb->token_costs[tx_size][type][ref][band][pt][t1];
+#endif
   UPDATE_RD_COST();
   best = rd_cost1 < rd_cost0;
   final_eob = i0 - 1;