i have written code in my application  it create recording but whole recording is black or blank it does not shoes the images 
 private void VideoCapture1_OnVideoFrameBitmap(object sender, VideoFrameBitmapEventArgs e)
        {
          
                Bitmap frame = testVideoRec;
         
            using (var grf = Graphics.FromImage(e.Frame))
            {
                var dur = e.StartTime / 1000;
               // var idx = dur % _images.Count;
                grf.DrawImage(frame, new Rectangle(0, 0, frame.Width, frame.Height), new Rectangle(0, 0, frame.Width, frame.Height), GraphicsUnit.Pixel);
                e.UpdateData = true;
            }
}
//////////////////////////////////////////////////
 var source = new ScreenCaptureSourceSettings
                {
                    Left = 0,
                    Right = 1280,
                    Top = 0,
                    Bottom = 960,
                    FrameRate = 15,
                    Mode = VFScreenCaptureMode.Color
                };
                VideoCapture1.Screen_Capture_Source = source;
                VideoCapture1.Audio_PlayAudio = false;
                VideoCapture1.Audio_RecordAudio = false;
                VideoCapture1.Mode = VFVideoCaptureMode.ScreenCapture;
                VideoCapture1.Output_Format = new VFMP4v8v10Output();
                VideoCapture1.Output_Filename = @"C:\Users\User\Documents\VisioForge\output34.mp4";
                VideoCapture1.Debug_Mode =false;
                VideoCapture1.Start();
///////
please check where it is wrong please help me