Windows Phone 8.1 MediaCapture freezes the phone

Question

I want to make a simple app that will allow me to check few parameters of every frame of preview, but I got stuck at running and stopping preview.

    /// <summary>     /// An empty page that can be used on its own or navigated to within a Frame.     /// </summary>     public sealed partial class MainPage : Page     {         MediaCapture _MediaCapture;         bool _recording;         public MainPage()         {             this.InitializeComponent();              this.NavigationCacheMode = NavigationCacheMode.Required;         }          /// <summary>         /// Invoked when this page is about to be displayed in a Frame.         /// </summary>         /// <param name="e">Event data that describes how this page was reached.         /// This parameter is typically used to configure the page.</param>         protected override async void OnNavigatedTo(NavigationEventArgs e)         {             var devices = await Windows.Devices.Enumeration.DeviceInformation.FindAllAsync(DeviceClass.VideoCapture);               var rearCamera = devices[0];             if (devices.Count > 0)             {                  rearCamera = devices.Single(currDev =>                   currDev.EnclosureLocation.Panel == Windows.Devices.Enumeration.Panel.Back                 );             }              _MediaCapture = new MediaCapture();             await _MediaCapture.InitializeAsync(new MediaCaptureInitializationSettings() { VideoDeviceId = rearCamera.Id });  // this is CaptureElement             xCapture.Source = _MediaCapture;              _recording = false;         }          protected override async void OnNavigatedFrom(NavigationEventArgs e)         {             if(_MediaCapture != null)             {                 await _MediaCapture.StopPreviewAsync();                 await _MediaCapture.StopRecordAsync();                  _MediaCapture.Dispose();                 _MediaCapture = null;                  xCapture.Source = null;             }               base.OnNavigatedFrom(e);           }  // button click handler         private async void StartMeasure(object sender, RoutedEventArgs e)         {             if (_recording)             {                 //await _MediaCapture.StopPreviewAsync();                 _MediaCapture.VideoDeviceController.TorchControl.Enabled = false;                 _recording = false;             }             else             {                 //await _MediaCapture.StartPreviewAsync();                 _MediaCapture.VideoDeviceController.TorchControl.Enabled = true;                 _recording = true;             }         }     } 

In this form it works perfectly.

If I uncomment those preview lines it works, but only once.

If I press the button three times: on, off and on again I get exception at line with enabling TorchControl.

System.Exception: Exception from HRESULT: 0xE801000D at Windows.Media.Devices.TorchControl.put_Enabled(Boolean value) at Pulsometr3.MainPage.d__d.MoveNext()

The HRESULT varies.

Whats even more weird, it sometimes freezes the phone (like 2 out of 3 times) and I need to hold Power + Volume Down.

I tried decorating all methods with [STAThread], but it didn't help (http://technet.microsoft.com/en-ca/br226599).

What's even more more interesting, when I hold operations by debbuger using F10 to step over lines I am able to toggle preview as many times as I possibly want. It's werid, since debugger hold all threads, right? So in theory there is no difference?

Also, phone sometimes freezes on deploy... And that's just annoying.

Any ideas?

Answer 1

I've got exactly into this...for some reason microsoft does not care much for it's successor OS to WP8, which makes me really sad. But it was also a half year ago during summer, I've tried this, maybe you can give a shot to googling on application consents and also double check your app manifests, if you have front/rear camera and webcam ticked in :) Besides that if it won't work, then bad luck, you are ought to stick with wp 8.0 version, which works exactly the same on wp 8.1 so do not worry :) also other libs like facebook stuff or parse.com won't work on wp 8.1 C# :)

Answer 2

I think your problem is the page cache enabled. Try to remove this line in your code this.NavigationCacheMode = NavigationCacheMode.Required;