How to detect camera preview is not working

Question

The preview code of an app is essentially the same as the example in the MSDN document for CaptureElement:

async void ShowPreview(object sender, RoutedEventArgs e)
{           
    if (mediaCaptureMgr == null)
    {              
        // Using Windows.Media.Capture.MediaCapture APIs 
        // to stream from webcam
        mediaCaptureMgr = new MediaCapture();
        await mediaCaptureMgr.InitializeAsync();

        myCaptureElement.Source = mediaCaptureMgr;
        await mediaCaptureMgr.StartPreviewAsync();
    }
}

It works most of the time, but fails occasionally. By "fails", I mean that I do not see the preview, but no exception is generated.  I am wondering if there is a way to determine whether the preview is working in the code. Many of the async function do not return anything, so I do not know what to check to ensure they return with success.   

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Hong

Answer 1

This is a tough scenario. If it fails only occasionally, I doubt that there's anything wrong with the code itself. It sounds like there's a non-UI thread that is getting an exception which does not bubble up and can't be caught.  Can you post a reproduction app so we can try to test this ourselves?

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Matt Small - Microsoft Escalation Engineer - Forum Moderator
If my reply answers your question, please mark this post as answered.

NOTE: If I ask for code, please provide something that I can drop directly into a project and run (including XAML), or an actual application project. I'm trying to help a lot of people, so I don't have time to figure out weird snippets with undefined objects and unknown namespaces.