use rounding in scaledown by 2

source/planar_functions.cc

 /*
  *  Copyright 2011 The LibYuv Project Authors. All rights reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS. All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 681 matching lines @@
   }
 #endif
 #if defined(HAS_SCALEROWDOWN2_NEON)
   if (TestCpuFlag(kCpuHasNEON)) {
     ScaleRowDown2 = ScaleRowDown2Box_Any_NEON;
     if (IS_ALIGNED(halfwidth, 16)) {
       ScaleRowDown2 = ScaleRowDown2Box_NEON;
     }
   }
 #endif
-#if defined(HAS_SCALEROWDOWN2_SSE2)
-  if (TestCpuFlag(kCpuHasSSE2)) {
-    ScaleRowDown2 = ScaleRowDown2Box_Any_SSE2;
+#if defined(HAS_SCALEROWDOWN2_SSSE3)
+  if (TestCpuFlag(kCpuHasSSSE3)) {
+    ScaleRowDown2 = ScaleRowDown2Box_Any_SSSE3;
     if (IS_ALIGNED(halfwidth, 16)) {
-      ScaleRowDown2 = ScaleRowDown2Box_SSE2;
+      ScaleRowDown2 = ScaleRowDown2Box_SSSE3;
     }
   }
 #endif
 #if defined(HAS_SCALEROWDOWN2_AVX2)
   if (TestCpuFlag(kCpuHasAVX2)) {
     ScaleRowDown2 = ScaleRowDown2Box_Any_AVX2;
     if (IS_ALIGNED(halfwidth, 32)) {
       ScaleRowDown2 = ScaleRowDown2Box_AVX2;
     }
   }
@@ skipping 1908 matching lines @@
     }
     free_aligned_buffer_64(rows);
   }
   return 0;
 }
 
 #ifdef __cplusplus
 }  // extern "C"
 }  // namespace libyuv
 #endif