UWP MediaFrameReader - System.ArgumentException: 'Value does not fall within the expected range.'


I am trying to create a UWP application that uses the laptop's webcam to process mediaframes on which I want to search faces using Microsoft Azure Face API.

I created a MediaCapture that works well, and a MediaFrameReader, which throws the exception mentioned in the question's title.

You can see my code here:

private async void StartDetection()
            mediaStream = new InMemoryRandomAccessStream();
            MediaEncodingProfile encodingProfile = MediaEncodingProfile.CreateMp4(encodingQuality);
            await mediaCapture.StartRecordToStreamAsync(encodingProfile, mediaStream);

            var frameSourceGroups = await MediaFrameSourceGroup.FindAllAsync();

            MediaFrameSourceGroup selectedGroup = null;
            MediaFrameSourceInfo colorSourceInfo = null;

            foreach (var sourceGroup in frameSourceGroups)
                foreach (var sourceInfo in sourceGroup.SourceInfos)
                    if (sourceInfo.MediaStreamType == MediaStreamType.VideoRecord
                        && sourceInfo.SourceKind == MediaFrameSourceKind.Color)
                        colorSourceInfo = sourceInfo;
                if (colorSourceInfo != null)
                    selectedGroup = sourceGroup;

            var selectedGroupObjects = frameSourceGroups.Select(group =>
                    sourceGroup = group,
                    colorSourceInfo = group.SourceInfos.FirstOrDefault((sourceInfo) =>
                        // On Xbox/Kinect, omit the MediaStreamType and EnclosureLocation tests
                        return sourceInfo.MediaStreamType == MediaStreamType.VideoRecord
                        && sourceInfo.SourceKind == MediaFrameSourceKind.Color
                        && sourceInfo.DeviceInformation?.EnclosureLocation.Panel == Windows.Devices.Enumeration.Panel.Front;

                }).Where(t => t.colorSourceInfo != null).FirstOrDefault();

            selectedGroup = selectedGroupObjects?.sourceGroup;
            colorSourceInfo = selectedGroupObjects?.colorSourceInfo;

            if (selectedGroup == null)

            var allGroups = await MediaFrameSourceGroup.FindAllAsync();
            var eligibleGroups = allGroups.Select(g => new
                Group = g,

                SourceInfos = new MediaFrameSourceInfo[]
                    g.SourceInfos.FirstOrDefault(info => info.SourceKind == MediaFrameSourceKind.Color),
                    g.SourceInfos.FirstOrDefault(info => info.SourceKind == MediaFrameSourceKind.Depth),
                    g.SourceInfos.FirstOrDefault(info => info.SourceKind == MediaFrameSourceKind.Infrared),
            }).Where(g => g.SourceInfos.Any(info => info != null)).ToList();

            if (eligibleGroups.Count == 0)
                System.Diagnostics.Debug.WriteLine("No source group with color, depth or infrared found.");

            var selectedGroupIndex = 0;
            selectedGroup = eligibleGroups[selectedGroupIndex].Group;
            colorSourceInfo = eligibleGroups[selectedGroupIndex].SourceInfos[0];
            MediaFrameSourceInfo infraredSourceInfo = eligibleGroups[selectedGroupIndex].SourceInfos[1];
            MediaFrameSourceInfo depthSourceInfo = eligibleGroups[selectedGroupIndex].SourceInfos[2];

            var colorFrameSource = mediaCapture.FrameSources[colorSourceInfo.Id];
            var preferredFormat = colorFrameSource.SupportedFormats.Where(format =>
                return format.VideoFormat.Width >= 1080
                && format.Subtype == "RGB24";


            if (preferredFormat == null)

            await colorFrameSource.SetFormatAsync(preferredFormat);

            MediaFrameReader mediaFrameReader;
            mediaFrameReader = await mediaCapture.CreateFrameReaderAsync(colorFrameSource, preferredFormat.Subtype);
            mediaFrameReader.FrameArrived += CheckFrameForFaces;
            await mediaFrameReader.StartAsync();

        private async void CheckFrameForFaces(MediaFrameReader sender, MediaFrameArrivedEventArgs args)
            var mediaFrame = sender.TryAcquireLatestFrame(); // -> this is the line that throws the exception
            var videoFrame = mediaFrame?.VideoMediaFrame;
            var bitmap = videoFrame?.SoftwareBitmap;

            WriteableBitmap wb = new WriteableBitmap(bitmap.PixelWidth, bitmap.PixelHeight);
            var img = Dlib.LoadImageData<RgbPixel>(wb.PixelBuffer.ToArray(), (uint)wb.PixelHeight, (uint)wb.PixelWidth, 3);
            ImageWindow im = new ImageWindow(img);

This code by the way is written based on the Microsoft documentation, which can be found here: https://docs.microsoft.com/en-us/windows/uwp/audio-video-camera/process-media-frames-with-mediaframereader

The only thing I changed is the MediaEncodingSubtype, because it didn't worked with Argb32, so I use Rgb24 (I checked all the supported formats in my computer). And I think the problem is derived from this property. When I initialize the MediaFrameReader object with the subtype Argb32 (as you can see in the documentation example) I get no exception, although the SoftwareBitmap will be null. On the other hand, if I use Rgb24 (because the preferredFormat has this subtype) I get the exception.

I can show some details of the exception:

  Message=Value does not fall within the expected range.
   at Windows.Media.Capture.Frames.MediaFrameReader.TryAcquireLatestFrame()
   at FaceAPI.MainPage.<CheckFrameForFaces>d__17.MoveNext() in P:\Dokumentumok\Suli\BME-VIK_6\Klitech\Házi feladat\KlitechHF\FaceAPI\FaceAPI\MainPage.xaml.cs:line 217
asked on Stack Overflow May 13, 2020 by pedro

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