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..505d59c5ea84b6933113819a9cdf420013250f36 100644
--- a/content/renderer/media/webrtc/video_destination_handler.cc
+++ b/content/renderer/media/webrtc/video_destination_handler.cc
@@ -41,6 +41,13 @@ class PpFrameWriter::FrameWriterDelegate
 
  private:
   friend class base::RefCountedThreadSafe<FrameWriterDelegate>;
+  // Endian in memory order, e.g. AXXX stands for uint8 pixel[4] = {A, x, x, x};
+  enum PixelEndian {
+    UNKNOWN,
+    AXXX,
+    XXXA,
+  };
+
   virtual ~FrameWriterDelegate();
 
   void StartDeliverOnIO(const VideoCaptureDeliverFrameCB& frame_callback);
@@ -52,9 +59,11 @@ class PpFrameWriter::FrameWriterDelegate
 
   scoped_refptr<base::MessageLoopProxy> io_message_loop_;
 
-  // |frame_pool_| and |new_frame_callback_| are only used on the IO-thread.
+  // |frame_pool_|, |new_frame_callback_| and |endian_| are only used on the
+  // IO-thread.
   media::VideoFramePool frame_pool_;
   VideoCaptureDeliverFrameCB new_frame_callback_;
+  PixelEndian endian_;
 
   // Used to DCHECK that we are called on the main render thread.
   base::ThreadChecker thread_checker_;
@@ -62,7 +71,7 @@ class PpFrameWriter::FrameWriterDelegate
 
 PpFrameWriter::FrameWriterDelegate::FrameWriterDelegate(
     const scoped_refptr<base::MessageLoopProxy>& io_message_loop_proxy)
-    : io_message_loop_(io_message_loop_proxy) {
+    : io_message_loop_(io_message_loop_proxy), endian_(UNKNOWN) {
 }
 
 PpFrameWriter::FrameWriterDelegate::~FrameWriterDelegate() {
@@ -101,6 +110,8 @@ 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 +164,46 @@ 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 a change in 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 in the first
+  // frame.
+  uint8* row_ptr = data;
+  // Note that we only do this if endian_ is still UNKNOWN.
+  for (int y = 0; y < height && endian_ == UNKNOWN; ++y) {
+    for (int x = 0; x < width; ++x) {
+      if (row_ptr[x * 4 + 0] != 255) {  // First byte is not Alpha => XXXA.
+        endian_ = XXXA;
+        break;
+      }
+      if (row_ptr[x * 4 + 3] != 255) {  // Fourth byte is not Alpha => AXXX.
+        endian_ = AXXX;
+        break;
+      }
+    }
+    row_ptr += stride;
+  }
+  if (endian_ == UNKNOWN) {
+    LOG(WARNING) << "PpFrameWriter::FrameWriterDelegate::DeliverFrameOnIO - "
+                 << "Could not determine endianness.";
+  }
+  // libyuv specifies fourcc/channel ordering the same as webrtc. That is why
+  // the naming is reversed compared to PixelEndian and PP_ImageDataFormat which
+  // describes the memory layout from the lowest address to the highest.
+  const auto* xxxxToI420 =
+      (endian_ == AXXX) ? &libyuv::BGRAToI420 : &libyuv::ARGBToI420;
+  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|.