Convert SoftwareBitmap to WriteableBitmap

Question

Everytime when i want to convert my SoftwareBitmap to a WriteableBitmap I get the following Exception: System.Runtime.InteropServices.COMException.

Here is my code snippet for that:

 private async void Start(object sender, RoutedEventArgs e)
        {

            _MediaCapture = new MediaCapture();
            await _MediaCapture.InitializeAsync();

            mediaElement.Source = _MediaCapture;
            await _MediaCapture.StartPreviewAsync();
            DispatcherTimer timer = new DispatcherTimer();
            timer.Interval = new TimeSpan(0, 0, 0, 1);
            timer.Tick += HandleTimerTick;
            timer.Start();
        }

        private async void HandleTimerTick(object Sender, object E)
        {


            var frame = await _MediaCapture.GetPreviewFrameAsync();
            SoftwareBitmap frameBitmap = frame.SoftwareBitmap;
            WriteableBitmap bitmap = new WriteableBitmap(frameBitmap.PixelWidth, frameBitmap.PixelHeight);
            try
            {
                frameBitmap.CopyToBuffer(bitmap.PixelBuffer);
            }
            catch (Exception)
            {
                Debug.WriteLine("Exception ");
            }
        }

The line

frameBitmap.CopyToBuffer(bitmap.PixelBuffer); 

is throwing the Exception.

I am debugging this on a x64 RemoteDevice.

Answer 1

I can reproduce this issue by using your code. It is caused by frame.SoftwareBitmap always returns null.

You can fix this issue by using the code as following:

    private async void button_Click(object sender, RoutedEventArgs e)
    {
        _mediaCapture = new MediaCapture();

        await _mediaCapture.InitializeAsync();

        mediaElement.Source = _mediaCapture;

        await _mediaCapture.StartPreviewAsync();

        DispatcherTimer timer = new DispatcherTimer();
        timer.Interval = new TimeSpan(0, 0, 0, 1);
        timer.Tick += Timer_Tick;
        timer.Start();
    }

    private async void Timer_Tick(object sender, object e)
    {
        var previewProperties = _mediaCapture.VideoDeviceController.GetMediaStreamProperties(MediaStreamType.VideoPreview) as VideoEncodingProperties;

        var videoFrame = new VideoFrame(BitmapPixelFormat.Bgra8, (int)previewProperties.Width, (int)previewProperties.Height);

        var frame = await _mediaCapture.GetPreviewFrameAsync(videoFrame);

        SoftwareBitmap frameBitmap = frame.SoftwareBitmap;

        WriteableBitmap bitmap = new WriteableBitmap(frameBitmap.PixelWidth, frameBitmap.PixelHeight);

        frameBitmap.CopyToBuffer(bitmap.PixelBuffer);

        Debug.WriteLine("done");
    }