public void Stop()
 {
     if (_cancelToken != null)
     {
         _cancelToken.Cancel();
         capGrabber = null;
     }
 }
        public void Start()
        {
            //creates new instance of the cancellationtoken
            _cancelToken = new CancellationTokenSource();

            Task.Factory.StartNew(() =>
            {
                // Create new grabber
                capGrabber = new CapGrabber();
                capGrabber.PropertyChanged += capGrabber_PropertyChanged;
                capGrabber.NewFrameArrived += capGrabber_NewFrameArrived;

                var graph = Activator.CreateInstance(Type.GetTypeFromCLSID(FilterGraph)) as IGraphBuilder;

                var sourceObject = FilterInfo.CreateFilter(deviceMoniker);

                var grabber       = Activator.CreateInstance(Type.GetTypeFromCLSID(SampleGrabber)) as ISampleGrabber;
                var grabberObject = grabber as IBaseFilter;

                if (graph == null)
                {
                    return;
                }

                graph.AddFilter(sourceObject, "source");
                graph.AddFilter(grabberObject, "grabber");
                using (var mediaType = new AMMediaType())
                {
                    mediaType.MajorType = MediaTypes.Video;
                    mediaType.SubType   = MediaSubTypes.RGB32;
                    if (grabber != null)
                    {
                        grabber.SetMediaType(mediaType);

                        if (graph.Connect(sourceObject.GetPin(PinDirection.Output, 0), grabberObject.GetPin(PinDirection.Input, 0)) >= 0)
                        {
                            if (grabber.GetConnectedMediaType(mediaType) == 0)
                            {
                                VideoInfoHeader header = (VideoInfoHeader)Marshal.PtrToStructure(mediaType.FormatPtr, typeof(VideoInfoHeader));
                                capGrabber.Width       = header.BmiHeader.Width;
                                capGrabber.Height      = header.BmiHeader.Height;
                            }
                        }
                        graph.Render(grabberObject.GetPin(PinDirection.Output, 0));
                        grabber.SetBufferSamples(false);
                        grabber.SetOneShot(false);
                        grabber.SetCallback(capGrabber, 1);
                    }

                    // Get the video window
                    var wnd = (IVideoWindow)graph;
                    wnd.put_AutoShow(false);

                    // Create the control and run
                    var control = (IMediaControl)graph;
                    control.Run();

                    // Wait for the stop signal
                    var stopSignal = new ManualResetEventSlim(false);
                    using (_cancelToken.Token.Register(stopSignal.Set))
                        stopSignal.Wait();

                    // Stop when ready
                    control.StopWhenReady();
                    capGrabber = null;
                }
            }, _cancelToken.Token);
        }