How to show live camera feed into SKXamlCanvas?

[hvansiaThor]

As the title mentions, I am trying to show live feed from the camera, connected via USB to my PC, into SKXamlCanvas. I am using C#, net8.0, WinUI and the library that I am using is SkiaSharp.Views.WinUI(2.88.6)

The following are two functions:

private void Camera_NewImageGrabbed(object? sender, EventArgs e)
{

    imagePtr = Camera.GetBuffer();
    Marshal.Copy(imagePtr, imageBuffer, 0, imageBuffer.Length);

    var gcHandle = GCHandle.Alloc(imageBuffer, GCHandleType.Pinned);
    bitmap = new SKBitmap();
    bitmap.InstallPixels(imageInfo, gcHandle.AddrOfPinnedObject(), imageInfo.RowBytes, delegate { gcHandle.Free(); }, null);

    Debug.WriteLine("Gray Value of first pixel: " + imageBuffer[0]);
    if(startRendering) { DispatcherQueue.TryEnqueue(() => skiaCanvas_PaintSurface(skiaCanvas, null)); }
   
}

private void skiaCanvas_PaintSurface(object sender, SkiaSharp.Views.Windows.SKPaintSurfaceEventArgs e)
{
    if( e != null)
    {
        canvas = e.Surface.Canvas;
        canvas.Clear(SKColors.AliceBlue);
        startRendering = true;
    }

    if(canvas != null && bitmap != null && e == null)
    {
        if(canvas.LocalClipBounds.Width > 0 && canvas.LocalClipBounds.Height > 0)
        {
            var destRect = SKRect.Create(0, 0, canvas.LocalClipBounds.Width, canvas.LocalClipBounds.Height);
            canvas.DrawBitmap(bitmap, destRect);
            bitmap.Dispose();
        }            
    }
}

If I comment out the line if(startRendering) { DispatcherQueue.TryEnqueue(() => skiaCanvas_PaintSurface(skiaCanvas, null));} I do not get any error. But left uncommented, I get error at the line "canvas.LocalClipBounds.Width". The error is "System.AccessViolationException: 'Attempted to read or write protected memory. This is often an indication that other memory is corrupt'". Can somebody help me understand why I am getting this error? How can I correct it? Also, if there is better implementation than what I have done above?

[hvansiaThor]

The following code mimics the camera live feed. If somebody wants to regenerate the error on their computer please use the following code. I am seeing same error as above.

MainWindow.xaml

<Window
    x:Class="WinUI_SkiaXamlCanvas.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:WinUI_SkiaXamlCanvas"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:skiasharp="using:SkiaSharp.Views.Windows"
    mc:Ignorable="d">

    <Grid>
        <skiasharp:SKXamlCanvas x:Name="skiaCanvas"
                    VerticalAlignment="Stretch"
                    HorizontalAlignment="Stretch"
                    PaintSurface="skiaCanvas_PaintSurface"
                    Margin="0 0 0 60">
        </skiasharp:SKXamlCanvas>
    </Grid>
</Window>

MainWindow.xaml.cs

    public sealed partial class MainWindow : Window
    {
        //DispatchTimer setup
        DispatcherTimer dispatchTimer;
        object xLock = new object();
        byte[] imageBuffer;
        SKImageInfo imageInfo;
        SKCanvas canvas;
        SKBitmap bitmap;

        public MainWindow()
        {
            InitializeComponent();
            imageBuffer = new byte[3840 * 2160];
            imageInfo = new SKImageInfo(3840, 2160, SKColorType.Gray8, SKAlphaType.Opaque);
            DispatcherTimerSetup();
        }

        public void DispatcherTimerSetup()
        {
            dispatchTimer = new DispatcherTimer();
            dispatchTimer.Tick += DispatchTimer_Tick;
            dispatchTimer.Interval = new TimeSpan(0, 0, 0, 0, 330);
            dispatchTimer.Start();
        }

        private void DispatchTimer_Tick(object sender, object e)
        {
            lock (xLock)
            {
                bitmap = new SKBitmap();
                byte value = 0;
                for (int i = 0; i < imageBuffer.Length; i++)
                {
                    imageBuffer[i] = value;
                    if (value != 255)
                        value++;
                    else
                        value = 0;
                }
                var gcHandle = GCHandle.Alloc(imageBuffer, GCHandleType.Pinned);
                bitmap.InstallPixels(imageInfo, gcHandle.AddrOfPinnedObject(), imageInfo.RowBytes, delegate { gcHandle.Free(); }, null);
                //DispatcherQueue.TryEnqueue(() => skiaCanvas_PaintSurface(skiaCanvas, null)); //Uncomment this for error
            }
        }

        private void skiaCanvas_PaintSurface(object sender, SkiaSharp.Views.Windows.SKPaintSurfaceEventArgs e)
        {
            if (e != null)
            {
                canvas = e.Surface.Canvas;
                canvas.Clear(SKColors.AliceBlue);
            }

            lock (xLock)
            {
                if (bitmap != null && canvas != null /*&& e == null*/) // Uncomment to get error
                {
                    canvas.DrawBitmap(bitmap, 0, 0);
                    Debug.WriteLine("Canvas drawn.");
                }
            }
        }
    }

[taublast]

I suspect when using DispatcherQueue.TryEnqueue like that several actions end up being executing at the same time and it might crash here, out of a lock:

canvas.Clear(SKColors.AliceBlue);