Document AR30 format

Bug: libyuv:751
Test: none
Change-Id: If6d5e7b9c5e6e8d2a272e03ce5a1cc199ef364ca
Reviewed-on: https://chromium-review.googlesource.com/779980Reviewed-by: Weiyong Yao <braveyao@chromium.org>
Reviewed-by: Frank Barchard <fbarchard@google.com>

README.chromium

 Name: libyuv
 URL: http://code.google.com/p/libyuv/
-Version: 1678
+Version: 1679
 License: BSD
 License File: LICENSE
 

docs/formats.md

@@ -54,6 +54,7 @@ The following is extracted from video_common.h as a complete list of formats sup
       FOURCC_ARGB = FOURCC('A', 'R', 'G', 'B'),
       FOURCC_BGRA = FOURCC('B', 'G', 'R', 'A'),
       FOURCC_ABGR = FOURCC('A', 'B', 'G', 'R'),
+      FOURCC_AR30 = FOURCC('A', 'R', '3', '0'),
       FOURCC_24BG = FOURCC('2', '4', 'B', 'G'),
       FOURCC_RAW  = FOURCC('r', 'a', 'w', ' '),
       FOURCC_RGBA = FOURCC('R', 'G', 'B', 'A'),
@@ -145,3 +146,13 @@ There are 2 RGB layouts - RGB24 (aka 24BG) and RAW
 
 RGB24 is B,G,R in memory
 RAW is R,G,B in memory
+
+# AR30
+
+AR30 is 2 10 10 10 ARGB stored in little endian order.
+The 2 bit alpha has 4 values.  Here are the comparable 8 bit alpha values.
+0 - 0.    00000000b = 0x00 = 0
+1 - 33%.  01010101b = 0x55 = 85
+2 - 66%.  10101010b = 0xaa = 170
+3 - 100%. 11111111b = 0xff = 255
+The 10 bit RGB values range from 0 to 1023.

include/libyuv/version.h

@@ -11,6 +11,6 @@
 #ifndef INCLUDE_LIBYUV_VERSION_H_
 #define INCLUDE_LIBYUV_VERSION_H_
 
-#define LIBYUV_VERSION 1678
+#define LIBYUV_VERSION 1679
 
 #endif  // INCLUDE_LIBYUV_VERSION_H_