Webcam frame to NSImage

Hello there,
I'm trying to port this Xamarin.iOS example to Xamarin.Mac sadly without success...
The "DidOutputSampleBuffer" gets called and I manage to repeatedly load an NSImage in a NSImageView, but if I try to load the webcam frame, nothing happens, no errors, no frames.
Should I modify the "ImageFromSampleBuffer" method?
Here is the relevant code:

public class OutputRecorder : AVCaptureVideoDataOutputSampleBufferDelegate
{
    public override void DidOutputSampleBuffer(AVCaptureOutput captureOutput, CMSampleBuffer sampleBuffer, AVCaptureConnection connection)
    {
        try
        {
            var image = ImageFromSampleBuffer(sampleBuffer);

            imgView.BeginInvokeOnMainThread(() => {
                var img = new NSImage(image, new CGSize(image.Width, image.Height));
                TryDispose(imgView.Image);
                // imgView.Image = NSImage.ImageNamed("testimage");     // This works!!!
                imgView.Image = img;                                // This doesn't work :-(
            });

        }
        catch (Exception e)
        {
            Console.WriteLine(e);
        }
        finally
        {
            sampleBuffer.Dispose();
        }
    }

    CGImage ImageFromSampleBuffer(CMSampleBuffer sampleBuffer)
    {
        // Get the CoreVideo image
        using (var pixelBuffer = sampleBuffer.GetImageBuffer() as CVPixelBuffer)
        {
            // Lock the base address
            pixelBuffer.Lock(CVPixelBufferLock.None);
            // Get the number of bytes per row for the pixel buffer
            var baseAddress = pixelBuffer.BaseAddress;
            var bytesPerRow = (int)pixelBuffer.BytesPerRow;
            var width = (int)pixelBuffer.Width;
            var height = (int)pixelBuffer.Height;
            var flags = CGBitmapFlags.PremultipliedFirst | CGBitmapFlags.ByteOrder32Little;
            // Create a CGImage on the RGB colorspace from the configured parameter above
            using (var cs = CGColorSpace.CreateDeviceRGB())
            {
                using (var context = new CGBitmapContext(baseAddress, width, height, 8, bytesPerRow, cs, (CGImageAlphaInfo)flags))
                {
                    using (CGImage cgImage = context.ToImage())
                    {
                        pixelBuffer.Unlock(CVPixelBufferLock.None);
                        return cgImage;
                    }
                }
            }
        }
    }

    void TryDispose(IDisposable obj)
    {
        if (obj != null)
            obj.Dispose();
    }
}