Как сделать захват axvlc в приложении windows пожалуйста

I want to take a photo from axVLCPlugin application
but all the photos I took were all black
Please help me

private void button1_Click(object sender, EventArgs e)
        {
            axVLCPlugin21.playlist.add("rtsp://admin:pana12345@10.10.1.70:554/cam/realmonitor?channel=1&subtype=0");
            pictureBox1.Visible = true;
             axVLCPlugin21.playlist.togglePause();
            Rectangle screenSize = new Rectangle(0,0,500,400);
             //Thread.Sleep(1000);
            Bitmap target = new Bitmap(screenSize.Width, screenSize.Height);
            //  Bitmap bmpSnapshot2= new Bitmap (700, 500);
            axVLCPlugin21.DrawToBitmap(target, screenSize);
            // Bitmap bmpSnapshot2 = new Bitmap(axVLCPlugin22.DrawToBitmap());
           
            pictureBox1.Image = target;
             axVLCPlugin21.playlist.play();
            pictureBox1.Image.Save(@"HinhCN\\kk.jpg");
        }