Camera video preview - Random crashes and green screens

Question

Hello everyone,
I am currently working on a Windows Phone 8.1 app and I need to preview video from the phone's back camera. For quite some time I've been struggling with random crashes and green screens. When these green screens appear, all camera apps become affected and
the device needs to be restarted. Occasionally the phone freezes and only recovers after battery removal. I test the app on my Lumia 620.
After some web search, I found references to the same problem by many users/developers of different apps. I'm really frustrated as I've tried many possible solutions with no avail.
Here is part of my code:
//in App.xaml.cs:
MediaCaptureInitializationSettings settings;
public static MediaCapture captureMgr;
public static bool UnableToInitializeCamera = false;
public async Task InitializeVideoCapture()
DeviceInformation backWebcam = await GetCameraDeviceInfoAsync(Windows.Devices.Enumeration.Panel.Back);
if(captureMgr!=null) captureMgr.Dispose();
captureMgr = new MediaCapture();
settings = new MediaCaptureInitializationSettings();
settings.StreamingCaptureMode = StreamingCaptureMode.Video;
settings.PhotoCaptureSource = PhotoCaptureSource.VideoPreview;
settings.AudioDeviceId = "";
if (backWebcam != null)
settings.VideoDeviceId = backWebcam.Id;
else
var _messageDialog = new MessageDialog("Back panel camera not found");
_messageDialog.Commands.Add(new UICommand("OK"));
_messageDialog.ShowAsync();
try
await captureMgr.InitializeAsync(settings);
captureMgr.SetPreviewRotation(VideoRotation.Clockwise90Degrees);
UnableToInitializeCamera = false;
catch
UnableToInitializeCamera = true;
Debug.WriteLine("HANDLED EXCEPTION: camera could not be initialized");
var _messageDialog = new MessageDialog("Unable to initialize camera");
_messageDialog.Commands.Add(new UICommand("OK"));
_messageDialog.ShowAsync();
protected override async void OnLaunched(LaunchActivatedEventArgs e)
//.... other app initialization code
await InitializeVideoCapture();
Window.Current.Activate();
private async void OnResuming(object sender, object e)
AppIsResuming = true;
FinishedCameraInitialize = false;
await Task.Delay(TimeSpan.FromSeconds(0.5));//this makes crashes less frequent
await InitializeVideoCapture();
FinishedCameraInitialize = true;
if(WasPreviewingCamera)
WasPreviewingCamera = false; //the following line allows time for SetupPage._captureElement to be assigned before video preview starts while (!SetupPage.CaptureElementSourceAssigned) await Task.Delay(TimeSpan.FromMilliseconds(1));
SetupPage.CaptureElementSourceAssigned = false;
try
Debug.WriteLine("trying to restart video preview");
await captureMgr.StartPreviewAsync();
SetupPage.PreviewingCamera = true;
catch
Debug.WriteLine("HANDLED EXCEPTION: unable to start previewing");
SetupPage.PreviewingCamera = false;
GC.Collect();
AppIsResuming = false;
private async void OnSuspending(object sender, SuspendingEventArgs e)
var deferral = e.SuspendingOperation.GetDeferral();
while (AppIsResuming) await Task.Delay(TimeSpan.FromMilliseconds(1));//prevents crash when app is suspended right after it is resumed
await CleanupCaptureResources();
TimeOfLastSuspend = DateTime.Now;
FinishedCameraInitialize = false;
GC.Collect();
deferral.Complete();
public async Task CleanupCaptureResources()
if (SetupPage.PreviewingCamera)
await captureMgr.StopPreviewAsync();
WasPreviewingCamera = true;
SetupPage.PreviewingCamera = false;
else WasPreviewingCamera = false;
if (captureMgr != null) captureMgr.Dispose();
//in SetupPage.xaml.cs
void OnSuspending(object sender, Windows.ApplicationModel.SuspendingEventArgs e)
var deferral = e.SuspendingOperation.GetDeferral();
_captureElement.Source = null;
CaptureElementSourceAssigned = false;
GC.Collect();
deferral.Complete();
private async void OnResuming(object sender, object e)
ProgressRing2.Visibility = Visibility.Visible;
ProgressRing2.IsActive = true;
while (!App.FinishedCameraInitialize) await Task.Delay(TimeSpan.FromMilliseconds(1));
App.FinishedCameraInitialize = false;
captureElement.Source = App.captureMgr;
CaptureElementSourceAssigned = true;
GC.Collect();
ProgressRing2.Visibility = Visibility.Collapsed;
ProgressRing2.IsActive = false;
Any help towards a solution will be greatly appreciated.
Thank you

Answer 1

I will also advice that you start by following the
Windows Store app sample.
Is this a Windows Phone app?
The crash/green screen only manifests itself when I suspend my app and switch to the default camera app (could be any other camera app perhaps). It happens roughly 1 out of 8 times. That's why I posted the suspension and resuming handlers, which I wrote
according to the msdn instructions.
I found
this page with a sample that demonstrates the MediaCapture API for Windows Phone. Some developers have reported problems similar as mine. Has Microsoft dealt with this issue?
I've spent quite a few weeks trying to investigate this problem, without actually knowing if it is my code that needs to be debugged. That's why I'm asking if other developers are facing similar problems.
Thank you
Edit: It seems that the crash/green screen can appear when suspending/switching to any app (regardless if it uses the camera or not). Also, all works fine when the app is running on the debugger.