commit 43edb7605669c5c59b2b6c3377d4c48018918987
author Dake He <dkhe@google.com> Thu Oct 26 10:29:46 2017 -0700
committer Dake He <dkhe@google.com> Thu Oct 26 14:31:42 2017 -0700
tree 0dde607f639d428e61156ef58f03f87e96425052
parent c7bf4fba655f97125091a4324f4ff50fb99c347d

[level map] separate pass to code signs

This commits moves coding of signs in a transform block into its own
pass. Grouping signs coded in literal mode together may help improve
throughput.

Change-Id: I999c6eeeb780b188ab9e2c6ea888f9de4dbce893

av1/decoder/decodetxb.c

diff --git a/av1/decoder/decodetxb.c b/av1/decoder/decodetxb.c
index 4d5edd7..5006b19 100644
--- a/av1/decoder/decodetxb.c
+++ b/av1/decoder/decodetxb.c
@@ -393,7 +393,6 @@
     update_eob = 0;
     for (c = *eob - 1; c >= 0; --c) {
       uint8_t *const level = &levels[scan[c]];
-      int8_t *const sign = &signs[scan[c]];
       int ctx;
 
       if (*level <= i) continue;
@@ -408,15 +407,6 @@
 
         if (counts) ++counts->coeff_base[txs_ctx][plane_type][i][ctx][1];
 
-        if (c == 0) {
-          int dc_sign_ctx = txb_ctx->dc_sign_ctx;
-          *sign = av1_read_record_bin(
-              counts, r, ec_ctx->dc_sign_cdf[plane_type][dc_sign_ctx], 2,
-              ACCT_STR);
-          if (counts) ++counts->dc_sign[plane_type][dc_sign_ctx][*sign];
-        } else {
-          *sign = av1_read_record_bit(counts, r, ACCT_STR);
-        }
         continue;
       }
       *level = i + 2;
@@ -427,22 +417,31 @@
     }
   }
 
-  for (c = update_eob; c >= 0; --c) {
-    uint8_t *const level = &levels[scan[c]];
+  // Loop to decode all signs in the transform block,
+  // starting with the sign of the DC (if applicable)
+  for (c = 0; c < *eob; ++c) {
     int8_t *const sign = &signs[scan[c]];
-    int idx;
-    int ctx;
-
-    if (*level <= NUM_BASE_LEVELS) continue;
-
+    if (levels[scan[c]] == 0) continue;
     if (c == 0) {
       int dc_sign_ctx = txb_ctx->dc_sign_ctx;
+#if LV_MAP_PROB
       *sign = av1_read_record_bin(
           counts, r, ec_ctx->dc_sign_cdf[plane_type][dc_sign_ctx], 2, ACCT_STR);
+#else
+      *sign = aom_read(r, ec_ctx->dc_sign[plane_type][dc_sign_ctx], ACCT_STR);
+#endif
       if (counts) ++counts->dc_sign[plane_type][dc_sign_ctx][*sign];
     } else {
       *sign = av1_read_record_bit(counts, r, ACCT_STR);
     }
+  }
+
+  for (c = update_eob; c >= 0; --c) {
+    uint8_t *const level = &levels[scan[c]];
+    int idx;
+    int ctx;
+
+    if (*level <= NUM_BASE_LEVELS) continue;
 
     ctx = get_br_ctx(levels, scan[c], bwl, height);