C# How to draw a overlay layer on Libvlcsharp videoview object?

Question

i need write some OSD information on my video i use libvlcsharp and videoview for play my videos. i saw when i play video, i can't access videos bitmap to draw some graphics on it this is my code and result thank for your help :)

   public partial class Form1 : Form
    {
        private LibVLC libVLC;
        private MediaPlayer mediaPlayer;

        public Form1()
        {
            InitializeComponent();
            libVLC = new LibVLC();
            mediaPlayer = new MediaPlayer(libVLC);
            var myMedia = new Media(libVLC, new Uri(@"C:\ffmpeg\Sample.mp4"));
            mediaPlayer.Media = myMedia;
            videoView1.MediaPlayer = mediaPlayer;
        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }

        private void cmdPlay_Click(object sender, EventArgs e)
        {
            if (videoView1.MediaPlayer.IsPlaying)
            {
                cmdPlay.Text = "Play";
                videoView1.MediaPlayer.Pause();
            }
            else
            {
                cmdPlay.Text = "Pause";
                videoView1.MediaPlayer.Play();
            }
        }

        private void videoView1_Paint(object sender, PaintEventArgs e)
        {
            Graphics g = e.Graphics;
            g.DrawString("Hello", new Font("Arial", 9, FontStyle.Bold), Brushes.White, new Point(10, 10));
        }

        private void cmdDrawOSD_Click(object sender, EventArgs e)
        {
            Graphics g = Graphics.FromHwnd(videoView1.Handle);
            g.DrawString("Hello", new Font("Arial", 9, FontStyle.Bold), Brushes.White, new Point(20, 20));
        }

        private void cmdRewind_Click(object sender, EventArgs e)
        {
            videoView1.MediaPlayer.Stop();
        }
    }

videoview paint event is working before play any video, if you play any video, this code not draw anythings on screen

        private void videoView1_Paint(object sender, PaintEventArgs e)
        {
            Graphics g = e.Graphics;
            g.DrawString("Hello", new Font("Arial", 9, FontStyle.Bold), Brushes.White, new Point(10, 10));
        }

i try to access videoview graphics by this code

            Graphics g = Graphics.FromHwnd(videoView1.Handle);
            g.DrawString("Hello", new Font("Arial", 9, FontStyle.Bold), Brushes.White, new Point(20, 20));

and it's work if you don't play video, when you play a video ,this code don't work and you can't see anythings happend on videoview object.

Result without play video Result when play video

thanks for your attention

I try to access graphics handle but not successfuly yet when video play all drawing disappear

Answer 1

You can try drawing another window (frameless topmost window) on top of the first one and sync the move/resizes event on top of it.

This is what is done in LibVLCSharp.WPF, but for WPF

Answer 2

You have to use the video callbacks for this, but you will have poor performance as it removes hardware decoding so you can interact with that bitmap from CPU. Here's a starting point https://github.com/mfkl/libvlcsharp-samples/blob/master/PreviewThumbnailExtractor/Program.cs

For the best performance, use the equivalent libvlc 4 api which uses direct3d or opengl directly.