Захват одного кадра с помощью directshow in VB.NET

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Привет
У меня есть какой-то код для захвата видео с веб-камеры. Как я мог бы захватить кадр из него в растровом формате?

 Enum PlayState
        init
        stopped
        paused
        running
    End Enum

    Dim currentState As PlayState = PlayState.stopped

    Dim d As Integer = Convert.ToInt32("0X8000", 16)
    Dim WM_GRAPHNOTIFY As Integer = d + 1
    Dim videoWindow As IVideoWindow = Nothing
    Dim mediaControl As IMediaControl = Nothing
    Dim mediaEventEx As IMediaEventEx = Nothing
    Dim graphBuilder As IGraphBuilder = Nothing
    Dim captureGraphBuilder As ICaptureGraphBuilder2 = Nothing
    Dim rot As DsROTEntry = Nothing

Private Sub startPreview()

        Dim sourceFilter As IBaseFilter = Nothing

        graphBuilder = CType(New FilterGraph, IGraphBuilder)
        captureGraphBuilder = CType(New CaptureGraphBuilder2, ICaptureGraphBuilder2)
        mediaControl = CType(graphBuilder, IMediaControl)
        videoWindow = CType(graphBuilder, IVideoWindow)
        mediaEventEx = CType(graphBuilder, IMediaEventEx)
        mediaEventEx.SetNotifyWindow(Me.Handle, WM_GRAPHNOTIFY, IntPtr.Zero)
        captureGraphBuilder.SetFiltergraph(graphBuilder)
        sampGrabber = CType(New SampleGrabber, ISampleGrabber)
        baseGrabFlt = CType(sampGrabber, IBaseFilter)

        Dim classEnum As IEnumMoniker = Nothing
        Dim moniker As IMoniker() = New IMoniker(0) {}
        Dim source As Object = Nothing
        Dim devEnum As ICreateDevEnum = CType(New CreateDevEnum, ICreateDevEnum)
        devEnum.CreateClassEnumerator(FilterCategory.VideoInputDevice, classEnum, 0)
        Marshal.ReleaseComObject(devEnum)

        If classEnum Is Nothing Then Throw New ApplicationException("No camera detected")

        If classEnum.Next(moniker.Length, moniker, IntPtr.Zero) = 0 Then
            moniker(0).BindToObject(Nothing, Nothing, GetType(IBaseFilter).GUID, source)
        Else
            Throw New ApplicationException("Detected camera is inaccessible")
        End If

        Marshal.ReleaseComObject(moniker(0))
        Marshal.ReleaseComObject(classEnum)

        sourceFilter = CType(source, IBaseFilter)

        graphBuilder.AddFilter(sourceFilter, "Video Capture")
        captureGraphBuilder.RenderStream(PinCategory.Preview, MediaType.Video, sourceFilter, Nothing, Nothing)
        Marshal.ReleaseComObject(sourceFilter)

        videoWindow.put_Owner(CAM1.Handle)
        videoWindow.put_WindowStyle(WindowStyle.Child Or WindowStyle.ClipChildren)
        videoWindow.SetWindowPosition(0, 0, CAM1.Width, CAM1.Height)
        videoWindow.put_Visible(OABool.True)

        rot = New DsROTEntry(graphBuilder)
        mediaControl.Run()
        currentState = PlayState.running

        CAM1Online = True

    End Sub

Что я уже пробовал:

Попробовал заглянуть в ISampleGrabber, но в VB ничего нет.

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