Exception when trying to check for auto focus support

Question

Hello,
In order to check some camera features at runtime, I'm using the code shown on this website (XAML) for my Windows Phone Silverlight 8.1 project:
http://developer.nokia.com/resources/library/Lumia/how-to-adapt-to-lumia-phone-hardware-features/how-to-check-availability-of-features-at-runtime.html#toc_Flashforcamera
if (mediaCapture.VideoDeviceController.FlashControl.Supported)
Checking all features in this way (flash, iso, torch, etc.) is working fine. However, when I'm trying to check any of the features in the area of "Regions of Interest Control",
my app crashes on a real devices, but not on any of the 8.1 emulators. Example coding, where the app crashes:
mediaCapture.VideoDeviceController.RegionsOfInterestControl.AutoFocusSupported
The exception is:
System.Exception: A device attached to the system is not functioning. (Exception from HRESULT: 0x8007001F)
Following this, I'v even tried to add all available capabilities to my app (in addition to "Webcam"), but without success.
Please find below my phone Information:
Nokia Lumia 620
Windows Phone 8.1
OS: 8.10.14192.280
FW: 3058.50000.1425.00006
Can you help to fix this issue?
Thanks and best regards,
Patrick

Answer 1

Hi Alan,
I did some more checks. Even with StartPreviewToCustomSinkAsync, the code crashes after a few seconds even when using the latest available developer firmware version
8.10.14219.341 on my Nokia Lumia 620.
Please find below the new coding and the exception being thrown as soon as I call an object from the RegionsOfInterestControl. Only the RegionsOfInterestControl causes the crash! Anything else works fine...
Exception:
+  $exception {System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.Exception: A device attached to the system is not functioning. (Exception from HRESULT: 0x8007001F)
   at Windows.Media.Devices.VideoDeviceController.get_RegionsOfInterestControl()
   at PhoNetInfo.ViewModels.MainViewModel.<LoadData_Camera>d__44.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.AsyncMethodBuilderCore.<ThrowAsync>b__3(Object state)
   --- End of inner exception stack trace ---
   at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor)
   at System.Reflection.RuntimeMethodInfo.UnsafeInvokeInternal(Object obj, Object[] parameters, Object[] arguments)
   at System.Reflection.RuntimeMethodInfo.UnsafeInvoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at System.Delegate.DynamicInvokeImpl(Object[] args)
   at System.Windows.Threading.DispatcherOperation.Invoke()} System.Exception {System.Reflection.TargetInvocationException}
Code:
            bool HasBackCamera = false;
            MediaCapture mediaCapture = null;
            var devices = await Windows.Devices.Enumeration.DeviceInformation.FindAllAsync(Windows.Devices.Enumeration.DeviceClass.VideoCapture);
            Windows.Devices.Enumeration.DeviceInformation backCameraDeviceInformation = devices.FirstOrDefault(x => x.EnclosureLocation != null && x.EnclosureLocation.Panel == Windows.Devices.Enumeration.Panel.Back);
            string backCameraId = null;
            var cameraIds = new List<string>();
            if (backCameraDeviceInformation != null)
                backCameraId = backCameraDeviceInformation.Id;
                HasBackCamera = true;
                cameraIds.Add(backCameraId);
            foreach (string cameraId in cameraIds)
                if (mediaCapture == null)
                    mediaCapture = new MediaCapture();
                    try
                        await mediaCapture.InitializeAsync(
                            new MediaCaptureInitializationSettings
                                VideoDeviceId = cameraId
                    catch (Exception e)
                        System.Diagnostics.Debug.WriteLine("Failed to initialize camera: " + e.ToString());
                        mediaCapture = null;
                        continue;
                if (mediaCapture.VideoDeviceController == null)
                    System.Diagnostics.Debug.WriteLine("No video device controller!");
                    continue;
                try
                    MediaCapturePreviewSink previewSink = new Windows.Phone.Media.Capture.MediaCapturePreviewSink();
                    var availableMediaStreamProperties = mediaCapture.VideoDeviceController.GetAvailableMediaStreamProperties(Windows.Media.Capture.MediaStreamType.VideoPreview)
                        .OfType<Windows.Media.MediaProperties.VideoEncodingProperties>()
                        .Where(p => p != null
                            && !String.IsNullOrEmpty(p.Subtype))
                        .ToList();
                    var previewFormat = availableMediaStreamProperties.FirstOrDefault();
                    await mediaCapture.VideoDeviceController.SetMediaStreamPropertiesAsync(Windows.Media.Capture.MediaStreamType.VideoPreview, previewFormat);
                    await mediaCapture.StartPreviewToCustomSinkAsync(new Windows.Media.MediaProperties.MediaEncodingProfile { Video = previewFormat }, previewSink);
                catch (Exception e)
                    System.Diagnostics.Debug.WriteLine("MediaCapture StartPreviewToCustomSinkAsync(): Failed to start preview: " + e.ToString());
                    mediaCapture = null;
                    continue;
  //the following line works
                bool hasFocus = mediaCapture.VideoDeviceController.FocusControl.Supported;
                //the following line causes the exception (RegionsOfInterestControl)
  bool hasAutoFocus = mediaCapture.VideoDeviceController.RegionsOfInterestControl.AutoFocusSupported;
                mediaCapture.Dispose();
                mediaCapture = null;