ppapi: Change endianness in libyuv calls, from BGRA to ARGB

content/renderer/media/webrtc/video_destination_handler.cc

Index: content/renderer/media/webrtc/video_destination_handler.cc
diff --git a/content/renderer/media/webrtc/video_destination_handler.cc b/content/renderer/media/webrtc/video_destination_handler.cc
index 160537165d7912e4c514f6d49272f9dd60d0adde..2d088301f565c0fe808154f4f453bc64c21fed28 100644
--- a/content/renderer/media/webrtc/video_destination_handler.cc
+++ b/content/renderer/media/webrtc/video_destination_handler.cc
@@ -101,6 +101,8 @@ void PpFrameWriter::FrameWriterDelegate::DeliverFrame(
                << "The image_data's mapped bitmap is NULL.";
     return;
   }
+  // We only support PP_IMAGEDATAFORMAT_BGRA_PREMUL at the moment.
+  DCHECK(image_data->format() == PP_IMAGEDATAFORMAT_BGRA_PREMUL);
   io_message_loop_->PostTaskAndReply(
       FROM_HERE,
       base::Bind(&FrameWriterDelegate::DeliverFrameOnIO, this,
@@ -153,15 +155,47 @@ void PpFrameWriter::FrameWriterDelegate::DeliverFrameOnIO(
       MediaStreamVideoSource::kUnknownFrameRate,
       media::PIXEL_FORMAT_YV12);
 
-  libyuv::BGRAToI420(data,
-                     stride,
-                     new_frame->data(media::VideoFrame::kYPlane),
-                     new_frame->stride(media::VideoFrame::kYPlane),
-                     new_frame->data(media::VideoFrame::kUPlane),
-                     new_frame->stride(media::VideoFrame::kUPlane),
-                     new_frame->data(media::VideoFrame::kVPlane),
-                     new_frame->stride(media::VideoFrame::kVPlane),
-                     frame_size.width(), frame_size.height());
+  // TODO(magjed): Remove this and always use libyuv::ARGBToI420 when
+  // crbug/426020 is fixed.
+  // Due to confusion about endianness, we try to determine it from the data.
+  // The alpha channel is always 255. It is unlikely for other color channels to
+  // be 255, so we will most likely break on the first few pixels.
+  enum {
+    UNKNOWN,
+    AXXX,
+    XXXA,
+  } endian = UNKNOWN;
+
+  uint8* row_ptr = data;
+  for (int y = 0; y < height && endian == UNKNOWN; ++y) {
+    for (int x = 0; x < width; ++x) {
+      if (row_ptr[x * 4 + 0] != 255) {
+        endian = XXXA;
+        break;
+      }
+      if (row_ptr[x * 4 + 3] != 255) {
+        endian = AXXX;
+        break;
+      }
+    }
+    row_ptr += stride;
+  }
+  if (endian == UNKNOWN) {
+    LOG(WARNING) << "PpFrameWriter::FrameWriterDelegate::DeliverFrameOnIO - "
+                 << "Could not determine endianness.";
+  }
+  const auto xxxxToI420 =
+      (endian == XXXA) ? libyuv::ARGBToI420 : libyuv::BGRAToI420;

[thorcarpenter, 2014/10/22 16:56:39]

can we do 

xxxToI420 = (endian == XXXA || endian == UNKNOWN) ? libyuv::ARGBToI420 :
libyuv::BGRAToI420;

Since ARGBToI420 is the future stable version of this code, and it's possible
for this code to make a mistake in the case of a pure blue frame, let's error on
the side of long term caution.

[magjed_chromium, 2014/10/22 17:27:53]

Done.

+  xxxxToI420(data,
+             stride,
+             new_frame->data(media::VideoFrame::kYPlane),
+             new_frame->stride(media::VideoFrame::kYPlane),
+             new_frame->data(media::VideoFrame::kUPlane),
+             new_frame->stride(media::VideoFrame::kUPlane),
+             new_frame->data(media::VideoFrame::kVPlane),
+             new_frame->stride(media::VideoFrame::kVPlane),
+             width,
+             height);
 
   // The local time when this frame is generated is unknown so give a null
   // value to |estimated_capture_time|.