Question

I am trying to provide an option to switch between webcams used to display preview using CaptureElement/MediaCapture. Unfortunately I tried multiple combinations of call sequences and the preview only shows up for the first device I use.

This is what I have been trying to do:

XAML:

<CaptureElement
    x:Name="captureElement"
    Stretch="UniformToFill" />

C#:

MediaCapture mediaCapture;
DeviceInformationCollection devices;
int currentDevice = 0;

private async void LayoutRoot_Tapped(object sender, Windows.UI.Xaml.Input.TappedEventArgs e)
{
    if (devices != null)
    {
        currentDevice = (currentDevice + 1) % devices.Count;
        InitializeWebCam();
    }
}

private async void InitializeWebCam()
{
    if (devices == null)
    {
        devices = await DeviceInformation.FindAllAsync(DeviceClass.VideoCapture);
        ListDeviceDetails();
    }

    if (mediaCapture != null)
    {
        await mediaCapture.StopPreviewAsync();

        this.captureElement.Source = null;
    }

    mediaCapture = new MediaCapture();
    await mediaCapture.InitializeAsync(
        new MediaCaptureInitializationSettings
        {
            VideoDeviceId = devices[currentDevice].Id
        });

    this.captureElement.Source = mediaCapture;
    await mediaCapture.StartPreviewAsync();
}

private void ListDeviceDetails()
{
    int i = 0;

    foreach (var device in devices)
    {
        Debug.WriteLine("* Device [{0}]", i++);
        Debug.WriteLine("EnclosureLocation.InDock: " + device.EnclosureLocation.InDock);
        Debug.WriteLine("EnclosureLocation.InLid: " + device.EnclosureLocation.InLid);
        Debug.WriteLine("EnclosureLocation.Panel: " + device.EnclosureLocation.Panel);
        Debug.WriteLine("Id: " + device.Id);
        Debug.WriteLine("IsDefault: " + device.IsDefault);
        Debug.WriteLine("IsEnabled: " + device.IsEnabled);
        Debug.WriteLine("Name: " + device.Name);
        Debug.WriteLine("IsDefault: " + device.IsDefault);

        foreach (var property in device.Properties)
        {
            Debug.WriteLine(property.Key + ": " + property.Value);
        }
    }
}

It seems like it does work to switch to second camera once in a while (below 10% of times) and then stays all black when I go back to the first one.

Sometimes the app hangs after I try to switch the camera once or twice (it stops responding to input, it is stuck in App.Run(), though the camera preview keeps refreshing).

Other times – it works in a way that it shows preview from the first device, but does not for the other one and when I go back to the first one – it works fine with it again.

Bugs?

There does not seem to be a Dispose or Uninitialize method anywhere. These are the properties I see (it’s Samsung’s Build 2011 tablet):

* Device [0]
EnclosureLocation.InDock: False
EnclosureLocation.InLid: False
EnclosureLocation.Panel: Front
Id: \\?\USB#VID_2232&PID_1021&MI_00#7&2469C269&0&0000#{e5323777-f976-4f5b-9b55-b94699c46e44}\GLOBAL
IsDefault: False
IsEnabled: True
Name: WebCam SC-20FHM11347N
IsDefault: False
System.ItemNameDisplay: WebCam SC-20FHM11347N
System.Devices.DeviceInstanceId: USB\VID_2232&PID_1021&MI_00\7&2469C269&0&0000
System.Devices.Icon: C:\Windows\System32\DDORes.dll,-2068
System.Devices.InterfaceEnabled: True
System.Devices.IsDefault: False
* Device [1]
EnclosureLocation.InDock: False
EnclosureLocation.InLid: False
EnclosureLocation.Panel: Back
Id: \\?\USB#VID_2232&PID_1022&MI_00#7&27072759&0&0000#{e5323777-f976-4f5b-9b55-b94699c46e44}\GLOBAL
IsDefault: False
IsEnabled: True
Name: WebCam SC-30H2L11449N
IsDefault: False
System.ItemNameDisplay: WebCam SC-30H2L11449N
System.Devices.DeviceInstanceId: USB\VID_2232&PID_1022&MI_00\7&27072759&0&0000
System.Devices.Icon: C:\Windows\System32\DDORes.dll,-2068
System.Devices.InterfaceEnabled: True
System.Devices.IsDefault: False

Answer 1

I think the problem must have been with the Developer Preview build. I have no problem switching between 3 web cams in the Consumer Preview one.