Scale specialized for 50/50 vertically and check x is integer

BUG=260
TESTED=manual test with LIBYUV_HEIGHT=1440
R=wuwang@google.com

Review URL: https://webrtc-codereview.appspot.com/2116004

git-svn-id: http://libyuv.googlecode.com/svn/trunk@772 16f28f9a-4ce2-e073-06de-1de4eb20be90

README.chromium

 Name: libyuv
 URL: http://code.google.com/p/libyuv/
-Version: 771
+Version: 772
 License: BSD
 License File: LICENSE
 

include/libyuv/version.h

@@ -11,6 +11,6 @@
 #ifndef INCLUDE_LIBYUV_VERSION_H_  // NOLINT
 #define INCLUDE_LIBYUV_VERSION_H_
 
-#define LIBYUV_VERSION 771
+#define LIBYUV_VERSION 772
 
 #endif  // INCLUDE_LIBYUV_VERSION_H_  NOLINT

source/row_common.cc

@@ -1792,6 +1792,14 @@ void ARGBAffineRow_C(const uint8* src_argb, int src_argb_stride,
   }
 }
 
+// Blend 2 rows into 1 for conversions such as I422ToI420.
+void HalfRow_C(const uint8* src_uv, int src_uv_stride,
+               uint8* dst_uv, int pix) {
+  for (int x = 0; x < pix; ++x) {
+    dst_uv[x] = (src_uv[x] + src_uv[src_uv_stride + x] + 1) >> 1;
+  }
+}
+
 // C version 2x2 -> 2x1.
 void InterpolateRow_C(uint8* dst_ptr, const uint8* src_ptr,
                       ptrdiff_t src_stride,
@@ -1800,6 +1808,10 @@ void InterpolateRow_C(uint8* dst_ptr, const uint8* src_ptr,
     memcpy(dst_ptr, src_ptr, width);
     return;
   }
+  if (source_y_fraction == 128) {
+    HalfRow_C(src_ptr, static_cast<int>(src_stride), dst_ptr, width);
+    return;
+  }
   int y1_fraction = source_y_fraction;
   int y0_fraction = 256 - y1_fraction;
   const uint8* src_ptr1 = src_ptr + src_stride;
@@ -1816,14 +1828,6 @@ void InterpolateRow_C(uint8* dst_ptr, const uint8* src_ptr,
   }
 }
 
-// Blend 2 rows into 1 for conversions such as I422ToI420.
-void HalfRow_C(const uint8* src_uv, int src_uv_stride,
-               uint8* dst_uv, int pix) {
-  for (int x = 0; x < pix; ++x) {
-    dst_uv[x] = (src_uv[x] + src_uv[src_uv_stride + x] + 1) >> 1;
-  }
-}
-
 // Select 2 channels from ARGB on alternating pixels.  e.g.  BGBGBGBG
 void ARGBToBayerRow_C(const uint8* src_argb,
                       uint8* dst_bayer, uint32 selector, int pix) {

source/scale_argb.cc

@@ -1468,7 +1468,7 @@ static void ScaleARGB(const uint8* src, int src_stride,
       }
     }
   }
-  if (dx == 0x10000 && (dx & 0xffff) == 0) {
+  if (dx == 0x10000 && (x & 0xffff) == 0) {
     // Arbitrary scale vertically, but unscaled vertically.
     ScaleARGBBilinearVertical(src_height,
                               clip_width, clip_height,