commit 037ee412117ec3ff47e6d3fc34e671840c7a3bf5
author David Barker <david.barker@argondesign.com> Tue Sep 19 12:43:46 2017 +0100
committer David Barker <david.barker@argondesign.com> Wed Sep 20 14:29:10 2017 +0000
tree d679b7e9d4dd85ef5fee25683954e2c9df042a84
parent db5d66feb6dfcdf9e57a85fe6e4d66d96086b4ee

new-multisymbol: Don't signal ext-comp-refs probs

Currently, when new-multisymbol and ext-comp-refs are
both enabled, the comp_ref_type_prob and uni_comp_ref_prob
arrays are forward updated in the compressed header, but
their values are never used.

We can save a tiny bit of space by not signalling the
forward updates at all; as a side benefit, we can wrap
the whole of read_frame_reference_mode_probs() in
a #if !CONFIG_NEW_MULTISYMBOL block.

Note: It seems the encoder already does this; I think
the reason it doesn't cause mismatches is because we
effectively pad the compressed header out to a full byte,
and av1_diff_update_prob() reads a bit with a very high
probability of being 0.

Change-Id: Ia1fca05ee498609c98c7ea1f89578f6783357d7f

av1/decoder/decodeframe.c

diff --git a/av1/decoder/decodeframe.c b/av1/decoder/decodeframe.c
index f1b19af..8492ad3 100644
--- a/av1/decoder/decodeframe.c
+++ b/av1/decoder/decodeframe.c
@@ -200,15 +200,11 @@
   }
 }
 
+#if !CONFIG_NEW_MULTISYMBOL
 static void read_frame_reference_mode_probs(AV1_COMMON *cm, aom_reader *r) {
-#if CONFIG_NEW_MULTISYMBOL && !CONFIG_EXT_COMP_REFS
-  (void)r;
-#else
   FRAME_CONTEXT *const fc = cm->fc;
   int i;
-#endif
 
-#if !CONFIG_NEW_MULTISYMBOL
   if (cm->reference_mode == REFERENCE_MODE_SELECT)
     for (i = 0; i < COMP_INTER_CONTEXTS; ++i)
       av1_diff_update_prob(r, &fc->comp_inter_prob[i], ACCT_STR);
@@ -221,7 +217,6 @@
       }
     }
   }
-#endif
 
   if (cm->reference_mode != SINGLE_REFERENCE) {
 #if CONFIG_EXT_COMP_REFS
@@ -235,7 +230,6 @@
     }
 #endif  // CONFIG_EXT_COMP_REFS
 
-#if !CONFIG_NEW_MULTISYMBOL
     for (i = 0; i < REF_CONTEXTS; ++i) {
       int j;
 #if CONFIG_EXT_REFS
@@ -248,11 +242,9 @@
         av1_diff_update_prob(r, &fc->comp_ref_prob[i][j], ACCT_STR);
 #endif  // CONFIG_EXT_REFS
     }
-#endif  // CONFIG_NEW_MULTISYMBOL
   }
 }
 
-#if !CONFIG_NEW_MULTISYMBOL
 static void update_mv_probs(aom_prob *p, int n, aom_reader *r) {
   int i;
   for (i = 0; i < n; ++i) av1_diff_update_prob(r, &p[i], ACCT_STR);
@@ -5061,7 +5053,9 @@
 
     if (cm->reference_mode != SINGLE_REFERENCE)
       setup_compound_reference_mode(cm);
+#if !CONFIG_NEW_MULTISYMBOL
     read_frame_reference_mode_probs(cm, &r);
+#endif
 
 #if CONFIG_EXT_INTER && CONFIG_COMPOUND_SINGLEREF
     for (i = 0; i < COMP_INTER_MODE_CONTEXTS; i++)