iOS: Optimize video scaling and cropping

webrtc/common_video/include/corevideo_frame_buffer.h

Index: webrtc/common_video/include/corevideo_frame_buffer.h
diff --git a/webrtc/common_video/include/corevideo_frame_buffer.h b/webrtc/common_video/include/corevideo_frame_buffer.h
index ed5361d5cf1f281ad26969fc1f98ee2123fc4f9d..2e108045c7d8309f25f5d7e864e59fe6c298d521 100644
--- a/webrtc/common_video/include/corevideo_frame_buffer.h
+++ b/webrtc/common_video/include/corevideo_frame_buffer.h
@@ -13,6 +13,8 @@
 
 #include <CoreVideo/CoreVideo.h>
 
+#include <vector>
+
 #include "webrtc/common_video/include/video_frame_buffer.h"
 
 namespace webrtc {
@@ -20,12 +22,32 @@ namespace webrtc {
 class CoreVideoFrameBuffer : public NativeHandleBuffer {
  public:
   explicit CoreVideoFrameBuffer(CVPixelBufferRef pixel_buffer);
+  CoreVideoFrameBuffer(CVPixelBufferRef pixel_buffer,
+                       int adapted_width,
+                       int adapted_height,
+                       int crop_width,
+                       int crop_height,
+                       int crop_x,
+                       int crop_y);
   ~CoreVideoFrameBuffer() override;
 
   rtc::scoped_refptr<VideoFrameBuffer> NativeToI420Buffer() override;
+  // Returns true if the internal pixel buffer needs to be cropped.
+  bool RequiresCropping() const;
+  // Crop and scales the internal pixel buffer to the output pixel buffer. The
+  // tmp buffer is used for intermediary splitting the UV channels. This
+  // function returns true if successful.
+  bool CropAndScaleTo(std::vector<uint8_t>* tmp_buffer,
+                      CVPixelBufferRef output_pixel_buffer) const;
 
  private:
   CVPixelBufferRef pixel_buffer_;
+  const int buffer_width_;

[tkchin_webrtc, 2016/10/19 00:48:32]

how is buffer width different from width/height of NativeHandleBuffer?

[magjed_webrtc, 2016/10/19 13:19:34]

I agree this is a bit confusing, but I don't see how I can easily make it
clearer. It works like this: buffer_width/height is the actual pixel buffer
resolution, the width/height in NativeHandleBuffer is the resolution we will
scale to. A generic external user should be unaware of the internal pixel buffer
size and only have to know what resolution NativeToI420Buffer() will have. So:
buffer_width >= crop_width >= width().

[tkchin_webrtc, 2016/10/19 22:50:17]

gotcha. Maybe short comment along those lines somewhere? (If this already exists
in a superclass that's fine too)

+  const int buffer_height_;
+  const int crop_width_;
+  const int crop_height_;
+  const int crop_x_;
+  const int crop_y_;
 };
 
 }  // namespace webrtc