adjust bias on Y channel so error histogram is better centered on green channel

BUG=324
TESTED=FullYUVTest
R=tpsiaki@google.com

Review URL: https://webrtc-codereview.appspot.com/38689004

git-svn-id: http://libyuv.googlecode.com/svn/trunk@1245 16f28f9a-4ce2-e073-06de-1de4eb20be90

README.chromium

 Name: libyuv
 URL: http://code.google.com/p/libyuv/
-Version: 1244
+Version: 1245
 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 1244
+#define LIBYUV_VERSION 1245
 
 #endif  // INCLUDE_LIBYUV_VERSION_H_  NOLINT

source/row_common.cc

@@ -962,8 +962,9 @@ void I400ToARGBRow_C(const uint8* src_y, uint8* dst_argb, int width) {
 
 // C reference code that mimics the YUV assembly.
 #define YG 19071 /* round(1.164 * 64 * 256) */
-#define YGB 1192  /* round(1.164 * 64 * 16) */
+#define YGB 1197 /* 1.164 * 64 * 16 - adjusted for even error distribution */
 
+// TODO(fbarchard): Adjusted U and V bias for even error distribution.
 #define UB -128 /* -min(128, round(2.018 * 64)) */
 #define UG 25 /* -round(-0.391 * 64) */
 #define UR 0
@@ -980,9 +981,9 @@ void I400ToARGBRow_C(const uint8* src_y, uint8* dst_argb, int width) {
 static __inline void YuvPixel(uint8 y, uint8 u, uint8 v,
                               uint8* b, uint8* g, uint8* r) {
   uint32 y1 = (uint32)(y * 0x0101 * YG) >> 16;
-  *b = Clamp((int32)(y1 - (v * VB + u * UB) + BB) >> 6);
-  *g = Clamp((int32)(y1 - (v * VG + u * UG) + BG) >> 6);
-  *r = Clamp((int32)(y1 - (v * VR + u * UR) + BR) >> 6);
+  *b = Clamp((int32)(BB - (v * VB + u * UB) + y1) >> 6);
+  *g = Clamp((int32)(BG - (v * VG + u * UG) + y1) >> 6);
+  *r = Clamp((int32)(BR - (v * VR + u * UR) + y1) >> 6);
 }
 
 #undef YG

source/row_win.cc

@@ -24,10 +24,11 @@ extern "C" {
 #if !defined(LIBYUV_DISABLE_X86) && defined(_MSC_VER) && \
     (defined(_M_IX86) || defined(_M_X64))
 
-// C reference code that mimics the YUV assembly.
+// YUV conversion constants.
 #define YG 19071 /* round(1.164 * 64 * 256) */
-#define YGB 1192  /* round(1.164 * 64 * 16) */
+#define YGB 1197 /* 1.164 * 64 * 16 - adjusted for even error distribution */
 
+// TODO(fbarchard): Adjusted U and V bias for even error distribution.
 #define UB -128 /* -min(128, round(2.018 * 64)) */
 #define UG 25 /* -round(-0.391 * 64) */
 #define UR 0