FakeVideoCaptureDevice: Regulate framerate without drifting

media/video/capture/fake_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.
 
 // Implementation of a fake VideoCaptureDevice class. Used for testing other
 // video capture classes when no real hardware is available.
 
 #ifndef MEDIA_VIDEO_CAPTURE_FAKE_VIDEO_CAPTURE_DEVICE_H_
 #define MEDIA_VIDEO_CAPTURE_FAKE_VIDEO_CAPTURE_DEVICE_H_
 
 #include <string>
 
 #include "base/atomicops.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
 #include "base/threading/thread.h"
 #include "base/threading/thread_checker.h"
+#include "base/time/time.h"
 #include "media/video/capture/video_capture_device.h"
 
 namespace media {
 
 class MEDIA_EXPORT FakeVideoCaptureDevice : public VideoCaptureDevice {
  public:
   enum FakeVideoCaptureDeviceType {
     USING_OWN_BUFFERS,
     USING_OWN_BUFFERS_TRIPLANAR,
     USING_CLIENT_BUFFERS_I420,
     USING_CLIENT_BUFFERS_GPU,
   };
 
   static int FakeCapturePeriodMs() { return kFakeCapturePeriodMs; }
 
   explicit FakeVideoCaptureDevice(FakeVideoCaptureDeviceType device_type);
   ~FakeVideoCaptureDevice() override;
 
   // VideoCaptureDevice implementation.
   void AllocateAndStart(const VideoCaptureParams& params,
                         scoped_ptr<Client> client) override;
   void StopAndDeAllocate() override;
 
  private:
   static const int kFakeCapturePeriodMs = 50;
 
-  void CaptureUsingOwnBuffers();
-  void CaptureUsingClientBuffers(VideoPixelFormat pixel_format);
-  void BeepAndScheduleNextCapture(const base::Closure& next_capture);
+  void CaptureUsingOwnBuffers(base::TimeTicks expected_execution_time);
+  void CaptureUsingClientBuffers(VideoPixelFormat pixel_format,
+                                 base::TimeTicks expected_execution_time);
+  void BeepAndScheduleNextCapture(
+      base::TimeTicks expected_execution_time,
+      const base::Callback<void(base::TimeTicks)>& next_capture);
 
   // |thread_checker_| is used to check that all methods are called in the
   // correct thread that owns the object.
   base::ThreadChecker thread_checker_;
 
   const FakeVideoCaptureDeviceType device_type_;
 
   scoped_ptr<VideoCaptureDevice::Client> client_;
   // |fake_frame_| is used for capturing on Own Buffers.
   scoped_ptr<uint8[]> fake_frame_;
   int frame_count_;
   VideoCaptureFormat capture_format_;
 
   // FakeVideoCaptureDevice post tasks to itself for frame construction and
   // needs to deal with asynchronous StopAndDeallocate().
   base::WeakPtrFactory<FakeVideoCaptureDevice> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(FakeVideoCaptureDevice);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_VIDEO_CAPTURE_FAKE_VIDEO_CAPTURE_DEVICE_H_