SharpGL with libmpv only voice no pictures

[lyg1949]

I use libmpv with SharpGL in a wpf desktop app.

no crash ,no error ,just no video only voice.

os: win7 x64 and win10 x64
visual studio 2019

did i miss something?

public MainWindow()
        {
            InitializeComponent();
            renderUpdateCallback = this.renderUpdate;
            GC.KeepAlive(renderUpdateCallback);
            mpvHandle = libmpv.mpv_create();
            libmpv.mpv_initialize(mpvHandle);
      }


private void OpenGLControl1_OpenGLInitialized(object sender, SharpGL.WPF.OpenGLRoutedEventArgs args)
        {
            createRender();
            libmpv.mpv_render_context_set_update_callback(mpvGLContext, renderUpdateCallback, IntPtr.Zero);
            libmpv.mpv_set_option_string(mpvHandle,"vo", "opengl-cb");
            libmpv.mpv_set_option_string(mpvHandle, "hwdec", "auto");
        }