This is the VideoCaptureDevice implementation for windows.

media/video/capture/win/video_capture_device_win.h

+// Copyright (c) 2011 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.
+
+// Windows specific implementation of VideoCaptureDevice.
+// DirectShow is used for capturing. DirectShow provide it's own threads
+// for capturing.
+
+#ifndef MEDIA_VIDEO_CAPTURE_WIN_VIDEO_CAPTURE_DEVICE_WIN_H_
+#define MEDIA_VIDEO_CAPTURE_WIN_VIDEO_CAPTURE_DEVICE_WIN_H_
+#pragma once
+
+// Avoid including strsafe.h via dshow as it will cause build warnings.
+#define NO_DSHOW_STRSAFE
+#include <dshow.h>
+
+#include <map>
+#include <string>
+
+#include "base/threading/thread.h"
+#include "base/win/scoped_com_initializer.h"
+#include "base/win/scoped_comptr.h"
+#include "media/video/capture/video_capture_device.h"
+#include "media/video/capture/win/sink_filter_win.h"
+#include "media/video/capture/win/sink_input_pin_win.h"
+
+namespace media {
+
+class VideoCaptureDeviceWin
+    : public VideoCaptureDevice,
+      public SinkFilterObserver {
+ public:
+  explicit VideoCaptureDeviceWin(const Name& device_name);
+  virtual ~VideoCaptureDeviceWin();
+  // Opens the device driver for this device.
+  // This function is used by the static VideoCaptureDevice::Create function.
+  bool Init();
+
+  // VideoCaptureDevice implementation.
+  virtual void Allocate(int width,
+                        int height,
+                        int frame_rate,
+                        VideoCaptureDevice::EventHandler* observer);
+  virtual void Start();
+  virtual void Stop();
+  virtual void DeAllocate();
+  virtual const Name& device_name();
+
+ private:
+  enum InternalState {
+    kIdle,  // The device driver is opened but camera is not in use.
+    kAllocated,  // The camera has been allocated and can be started.
+    kCapturing,  // Video is being captured.
+    kError  // Error accessing HW functions.
+            // User needs to recover by destroying the object.
+  };
+  typedef std::map<int, Capability> CapabilityMap;
+
+  // Implements SinkFilterObserver.
+  virtual void FrameReceived(const uint8* buffer, int length);
+
+  bool CreateCapabilityMap();
+  int GetBestMatchedCapability(int width, int height, int frame_rate);
+  void SetErrorState(const char* reason);
+
+  base::win::ScopedCOMInitializer initialize_com_;
+
+  Name device_name_;
+  InternalState state_;
+  VideoCaptureDevice::EventHandler* observer_;
+
+  base::win::ScopedComPtr<IBaseFilter> capture_filter_;
+  base::win::ScopedComPtr<IGraphBuilder> graph_builder_;
+  base::win::ScopedComPtr<IMediaControl> media_control_;
+  base::win::ScopedComPtr<IPin> input_sink_pin_;
+  base::win::ScopedComPtr<IPin> output_capture_pin_;
+  // Used when using a MJPEG decoder.
+  base::win::ScopedComPtr<IBaseFilter> mjpg_filter_;
+  base::win::ScopedComPtr<IPin> input_mjpg_pin_;
+  base::win::ScopedComPtr<IPin> output_mjpg_pin_;
+
+  scoped_refptr<SinkFilter> sink_filter_;
+
+  // Map of all capabilities this device support.
+  CapabilityMap capabilities_;
+
+  DISALLOW_IMPLICIT_CONSTRUCTORS(VideoCaptureDeviceWin);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_VIDEO_CAPTURE_WIN_VIDEO_CAPTURE_DEVICE_WIN_H_