Sporadic Render hang

Geetha 1

Hi All,

Sporadically either RenderOpen or Render method hangs and does not execute further.

Below is code snippet, we have tried using SoftwareOnly render mode also. But issue still persists.

RenderTargetBitmap rtb = new RenderTargetBitmap(320, 240, 96, 96, PixelFormats.Pbgra32);
DrawingVisual dv = new DrawingVisual();
using (DrawingContext dc = dv.RenderOpen())
{
	dc.DrawVideo(player, new Rect(0, 0, 320, 240)); // player is of WindowsMediaPlayer
}
rtb.Render(dv);

Hui Liu-MSFT 47,341 Reputation points Microsoft Vendor

2023-07-25T05:39:57.2666667+00:00
Hi,@GeethaPriya Balaraman.Welcome Microsoft Q&A.

The issue you're encountering with the RenderTargetBitmap.Render() method hanging could be related to a deadlock or some other blocking operation happening in your application. To help troubleshoot and resolve this issue, you can try the following steps:

Check for Deadlocks: Make sure there are no potential deadlocks in your application. Deadlocks can occur when multiple threads are trying to access shared resources concurrently. Ensure that you are not calling the RenderTargetBitmap.Render() method from a UI thread that might be blocked or waiting for some other operation to complete.

Verify player Object: Ensure that the player object (WindowsMediaPlayer) is properly initialized and accessible when rendering. If there's any issue with the player object, it might lead to the rendering process getting stuck.

Threading Issues: Check if there are any threading issues in your application. Ensure that you are not blocking the UI thread while attempting to render the bitmap.

Use Dispatcher: If you are calling the rendering code from a non-UI thread, consider using the Dispatcher to marshal the rendering operation to the UI thread.

// Assuming you are calling this code from a non-UI thread Application.Current.Dispatcher.Invoke(() => { RenderTargetBitmap rtb = new RenderTargetBitmap(320, 240, 96, 96, PixelFormats.Pbgra32); DrawingVisual dv = new DrawingVisual(); using (DrawingContext dc = dv.RenderOpen()) { dc.DrawVideo(player, new Rect(0, 0, 320, 240)); // player is of WindowsMediaPlayer } rtb.Render(dv); });

If there are still problems, can you use animation to show the problem?

Geetha 1

Hi Hui Liu-MSFT,

Thanks for your response. Code is run under WCF service in backend and no UI is involved. Usecase performed is - open video, pause and set player position, draw video and create bitmap file (.png)

Below is draft code:

				var player = new MediaPlayer { Volume = 0, ScrubbingEnabled = true };
                var wMPlayer = new WindowsMediaPlayer();
                try
                {
                    var clip = wMPlayer.newMedia(uri);
                    var videoDuration = (int)TimeSpan.FromSeconds(clip.duration).TotalSeconds;
                    
                    player.Open(new Uri(uri));
                    player.Pause();
                    
                    TimeSpan quarterDuration = TimeSpan.FromSeconds(videoDuration * 0.25);
                    player.Position = quarterDuration;
                                     
                    Thread.Sleep(4500);                    
                    RenderTargetBitmap rtb = new RenderTargetBitmap(320, 240, 96, 96, PixelFormats.Pbgra32);                    
                    DrawingVisual dv = new DrawingVisual();
                    
                    using (DrawingContext dc = dv.RenderOpen())
                    {                        
                        dc.DrawVideo(player, new Rect(0, 0, 320, 240));                        
                    }
                    
                    rtb.Render(dv);                   
                    BitmapFrame frame = BitmapFrame.Create(rtb).GetCurrentValueAsFrozen() as BitmapFrame;
                    BitmapEncoder encoder = new PngBitmapEncoder();
                    encoder.Frames.Add(frame);
                    using (MemoryStream memoryStream = new MemoryStream())
                    {
                        encoder.Save(memoryStream);
						File.WriteAllBytes(previewIcon, memoryStream.ToArray());                        
                    }
                }
                finally
                {
                    player.Close();
                    wMPlayer.close();
                }

Viorel 114.7K Reputation points

2023-07-27T06:56:29.9866667+00:00

Maybe these objects and functions are not designed to work inside services.

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Sporadic Render hang