Bug 1778405 - Correct Cb, Cr in YUVBufferGenerator::CreateNV{12,21}Im…

…age() r=jgilbert,jolin

The first element in the NV12's UV plane and NV21's one should be mapped
to Cb and Cr respectively.

Differential Revision: https://phabricator.services.mozilla.com/D151186

dom/media/gtest/YUVBufferGenerator.cpp

@@ -59,12 +59,12 @@ Image* YUVBufferGenerator::CreateI420Image() {
   data.mYStride = mImageSize.width;
   data.mYSkip = 0;
 
-  // Cr plane.
+  // Cr plane (aka V).
   uint8_t* cr = y + yPlaneSize + uvPlaneSize;
   data.mCrChannel = cr;
   data.mCrSkip = 0;
 
-  // Cb plane
+  // Cb plane (aka U).
   uint8_t* cb = y + yPlaneSize;
   data.mCbChannel = cb;
   data.mCbSkip = 0;
@@ -92,16 +92,16 @@ Image* YUVBufferGenerator::CreateNV12Image() {
   data.mYStride = mImageSize.width;
   data.mYSkip = 0;
 
-  // Cr plane.
-  uint8_t* cr = y + yPlaneSize;
-  data.mCrChannel = cr;
-  data.mCrSkip = 1;
-
-  // Cb plane
-  uint8_t* cb = y + yPlaneSize + 1;
+  // Cb plane (aka U).
+  uint8_t* cb = y + yPlaneSize;
   data.mCbChannel = cb;
   data.mCbSkip = 1;
 
+  // Cr plane (aka V).
+  uint8_t* cr = y + yPlaneSize + 1;
+  data.mCrChannel = cr;
+  data.mCrSkip = 1;
+
   // 4:2:0.
   data.mCbCrStride = mImageSize.width;
   data.mChromaSubsampling = gfx::ChromaSubsampling::HALF_WIDTH_AND_HEIGHT;
@@ -123,16 +123,16 @@ Image* YUVBufferGenerator::CreateNV21Image() {
   data.mYStride = mImageSize.width;
   data.mYSkip = 0;
 
-  // Cr plane.
-  uint8_t* cr = y + yPlaneSize + 1;
-  data.mCrChannel = cr;
-  data.mCrSkip = 1;
-
-  // Cb plane
-  uint8_t* cb = y + yPlaneSize;
+  // Cb plane (aka U).
+  uint8_t* cb = y + yPlaneSize + 1;
   data.mCbChannel = cb;
   data.mCbSkip = 1;
 
+  // Cr plane (aka V).
+  uint8_t* cr = y + yPlaneSize;
+  data.mCrChannel = cr;
+  data.mCrSkip = 1;
+
   // 4:2:0.
   data.mCbCrStride = mImageSize.width;
   data.mChromaSubsampling = gfx::ChromaSubsampling::HALF_WIDTH_AND_HEIGHT;