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BITSTREAM - CLARIFICATION OF MV SIZE RANGE

The codec should effectively run with motion vector of range (-2048, 2047)
in full pixels, for sequences of 1080p and below. Add assertions to clarify
this behavior.

Change-Id: Ia0cac28249f587d8f8882205228fa480263ab313

--- a/vp9/common/vp9_entropymv.h

+++ b/vp9/common/vp9_entropymv.h

@@ -73,6 +73,10 @@

 #define MV_MAX         ((1 << MV_MAX_BITS) - 1)

 #define MV_VALS        ((MV_MAX << 1) + 1)

+#define MV_IN_USE_BITS 14

+#define MV_UPP   ((1 << MV_IN_USE_BITS) - 1)

+#define MV_LOW   (-(1 << MV_IN_USE_BITS))

+

 extern const vp9_tree_index vp9_mv_class0_tree[2 * CLASS0_SIZE - 2];

 extern struct vp9_token vp9_mv_class0_encodings[CLASS0_SIZE];

--- a/vp9/decoder/vp9_decodemv.c

+++ b/vp9/decoder/vp9_decodemv.c

@@ -522,8 +522,14 @@

             assert(!"Invalid inter mode value");

         }

         mi->bmi[j].as_mv[0].as_int = block[0].as_int;

-        if (is_compound)

+        assert(block[0].as_mv.row < MV_UPP && block[0].as_mv.row > MV_LOW);

+        assert(block[0].as_mv.col < MV_UPP && block[0].as_mv.col > MV_LOW);

+

+        if (is_compound) {

           mi->bmi[j].as_mv[1].as_int = block[1].as_int;

+          assert(block[1].as_mv.row < MV_UPP && block[1].as_mv.row > MV_LOW);

+          assert(block[1].as_mv.col < MV_UPP && block[1].as_mv.col > MV_LOW);

+        }

         if (num_4x4_h == 2)

           mi->bmi[j + 2] = mi->bmi[j];

@@ -563,6 +569,12 @@

         break;

       default:

         assert(!"Invalid inter mode value");

+    }

+    assert(mv0->as_mv.row < MV_UPP && mv0->as_mv.row > MV_LOW);

+    assert(mv0->as_mv.col < MV_UPP && mv0->as_mv.col > MV_LOW);

+    if (is_compound) {

+      assert(mv1->as_mv.row < MV_UPP && mv1->as_mv.row > MV_LOW);

+      assert(mv1->as_mv.col < MV_UPP && mv1->as_mv.col > MV_LOW);

     }

   }

 }