问MediaFrameReader在设置MJPG格式时抛出ArgementException？

EN

private async Task StartReadFrameAsync()
{
    MediaFrameSourceInfo colorSourceInfo = null;
    MediaFrameSourceGroup selectedGroup = null;
    var frameSourceGroups = await MediaFrameSourceGroup.FindAllAsync();
    foreach (var sourceGroup in frameSourceGroups)
    {
        foreach (var sourceInfo in sourceGroup.SourceInfos)
        {
            if (sourceInfo.MediaStreamType == MediaStreamType.VideoRecord && sourceInfo.SourceKind == MediaFrameSourceKind.Color)
            {
                colorSourceInfo = sourceInfo;
                break;
            }
        }
        if (colorSourceInfo != null)
        {
            selectedGroup = sourceGroup;
            break;
        }
    }

    var settings = new MediaCaptureInitializationSettings
            {
                VideoDeviceId = deviceId, 
                SourceGroup = selectedGroup, 
                MemoryPreference = MediaCaptureMemoryPreference.Cpu
            };
    var mediaCapture = new MediaCapture();
    await mediaCapture.InitializeAsync(settings);

    var colorFrameSource = mediaCapture.FrameSources[colorSourceInfo.Id];
    var preferredFormat = colorFrameSource.SupportedFormats.FirstOrDefault(format =>
    {
        return format.Subtype == MediaEncodingSubtypes.Mjpg && format.VideoFormat.Width >= 720;
    });
    if (preferredFormat == null)    
         return;    

    await colorFrameSource.SetFormatAsync(preferredFormat);
    mediaFrameReader = await mediaCapture.CreateFrameReaderAsync(colorFrameSource, MediaEncodingSubtypes.Mjpg);
    mediaFrameReader.FrameArrived += MediaFrameReader_FrameArrived;
    await mediaFrameReader.StartAsync();
}

private async void MediaFrameReader_FrameArrived(MediaFrameReader sender, MediaFrameArrivedEventArgs args)
{
    var mediaFrameReference = sender.TryAcquireLatestFrame();  // <- throws ArgementException 
    var videoMediaFrame = mediaFrameReference?.VideoMediaFrame;
    var softwareBitmap = videoMediaFrame?.SoftwareBitmap;
    //...
}