Improve the accuracy YUV to RGB for ARMv7 NEON

NEON version of YUV422TORGB is updated based on C algorithm. Accuracy YUV to RGB
of NEON is also updated according to test result. Macro LIBYUV_NEON is added to
identify accuracy YUV to RGB for ARM platform.
Except TestJ420 and TestYUV, all the other tests are passed.

BUG=324
TESTED=libyuvTest on ARMv7 with Android
R=fbarchard@google.com

Change-Id: I492ca628679940534f40341721dc5b6dc2d7a5b6

Review URL: https://webrtc-codereview.appspot.com/40609004

git-svn-id: http://libyuv.googlecode.com/svn/trunk@1296 16f28f9a-4ce2-e073-06de-1de4eb20be90

libyuv_test.gyp

@@ -76,6 +76,16 @@
             'HAVE_JPEG',
           ],
         }],
+        # TODO(YangZhang): These lines can be removed when high accuracy
+        # YUV to RGB to Neon is ported.
+        [ '(target_arch == "armv7" or target_arch == "armv7s" \
+          or (target_arch == "arm" and arm_version >= 7) \
+          or target_arch == "arm64") \
+          and (arm_neon == 1 or arm_neon_optional == 1)', {
+          'defines': [
+            'LIBYUV_NEON'
+          ],
+       }],
       ], # conditions
     },
 

unit_test/color_test.cc

@@ -24,11 +24,11 @@ namespace libyuv {
 // TODO(fbarchard): Port high accuracy YUV to RGB to Neon.
 #if !defined(LIBYUV_DISABLE_NEON) && \
     (defined(__aarch64__) || defined(__ARM_NEON__) || defined(LIBYUV_NEON))
-#define MAX_CDIFF 2
-#define ERROR_R 3
-#define ERROR_G 3
-#define ERROR_B 5
-#define ERROR_FULL 7
+#define MAX_CDIFF 0
+#define ERROR_R 1
+#define ERROR_G 1
+#define ERROR_B 3
+#define ERROR_FULL 6
 #else
 #define MAX_CDIFF 0
 #define ERROR_R 1