Video capture: Refactor GetBestMatchedFormat from Win to OS independent

media/video/capture/video_capture_device.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 //
 // VideoCaptureDevice is the abstract base class for realizing video capture
 // device support in Chromium. It provides the interface for OS dependent
 // implementations.
 // The class is created and functions are invoked on a thread owned by
 // VideoCaptureManager. Capturing is done on other threads, depending on the OS
 // specific implementation.
 
 #ifndef MEDIA_VIDEO_CAPTURE_VIDEO_CAPTURE_DEVICE_H_
 #define MEDIA_VIDEO_CAPTURE_VIDEO_CAPTURE_DEVICE_H_
 
+#include <stdint.h>
 #include <list>
 #include <string>
 
 #include "base/logging.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/single_thread_task_runner.h"
 #include "base/time/time.h"
 #include "media/base/media_export.h"
 #include "media/base/video_frame.h"
@@ skipping 292 matching lines @@
   //
   // This function must be called between InitializeImageCapture() and
   // ReleaseImageCapture().
   virtual void CaptureImage() {}
 
  protected:
   static const int kPowerLine50Hz = 50;
   static const int kPowerLine60Hz = 60;
 };
 
+// Helper function to compare video capture formats when finding the most
+// closely matched video format given a requested video format.
+// Smaller difference means more closely matched formats.
+// Prioritizes according to this list:
+// 1. Closest matching height.
+// 2. Closest matching width.
+// 3. Closest matching frame rate.
+// 4. Best color format.
+// Nr 4. is not commutative, i.e. the order of the inputs to this
+// function matters.
+uint64_t DiffVideoCaptureFormat(const VideoCaptureFormat& requested,
+                                const VideoCaptureFormat& supported);
+
 }  // namespace media
 
 #endif  // MEDIA_VIDEO_CAPTURE_VIDEO_CAPTURE_DEVICE_H_