[x265] [PATCH] bitcost: avoid overflow when mvx and mvy costs are added together

[deepthi at multicorewareinc.com]

# HG changeset patch
# User Deepthi Nandakumar <deepthi at multicorewareinc.com>
# Date 1436172175 -19800
#      Mon Jul 06 14:12:55 2015 +0530
# Node ID 0497a2dd6a2a20eaaac3c57302b3bc7f103f0854
# Parent  bf57ce5d38d5208a491bf4192e389ab1eb4a4f32
bitcost: avoid overflow when mvx and mvy costs are added together

This will prevent overflow and wrap-around errors, giving erroneously low mvcosts.

diff -r bf57ce5d38d5 -r 0497a2dd6a2a source/encoder/bitcost.cpp
--- a/source/encoder/bitcost.cpp	Fri Jul 03 19:50:02 2015 +0530
+++ b/source/encoder/bitcost.cpp	Mon Jul 06 14:12:55 2015 +0530
@@ -45,7 +45,7 @@
 
             // estimate same cost for negative and positive MVD
             for (int i = 0; i <= 2 * BC_MAX_MV; i++)
-                s_costs[qp][i] = s_costs[qp][-i] = (uint16_t)X265_MIN(s_bitsizes[i] * lambda + 0.5f, (1 << 16) - 1);
+                s_costs[qp][i] = s_costs[qp][-i] = (uint16_t)X265_MIN(s_bitsizes[i] * lambda + 0.5f, (1 << 15) - 1);
         }
     }