Media casting

This article shows you how to cast media to remote devices from a Universal Windows app.

Built-in media casting with MediaPlayerElement

The simplest way to cast media from a Universal Windows app is to use the built-in casting capability of the MediaPlayerElement control.

To allow the user to open a video file to be played in the MediaPlayerElement control, add the following namespaces to your project.

using Windows.Storage;
using Windows.Storage.Pickers;
using Windows.Storage.Streams;
using Windows.Media.Core;

In your app's XAML file, add a MediaPlayerElement and set AreTransportControlsEnabled to true.

<MediaPlayerElement Name="mediaPlayerElement"  MinHeight="100" MaxWidth="600" HorizontalAlignment="Stretch" AreTransportControlsEnabled="True"/>

Add a button to let the user initiate picking a file.

<Button x:Name="openButton" Click="openButton_Click" Content="Open"/>

In the Click event handler for the button, create a new instance of the FileOpenPicker, add video file types to the FileTypeFilter collection, and set the starting location to the user's videos library.

Call PickSingleFileAsync to launch the file picker dialog. When this method returns, the result is a StorageFile object representing the video file. Check to make sure the file isn't null, which it will be if the user cancels the picking operation. Call the file's OpenAsync method to get an IRandomAccessStream for the file. Finally, create a new MediaSource object from the selected file by calling CreateFromStorageFile and assign it to the MediaPlayerElement object's Source property to make the video file the video source for the control.

private async void openButton_Click(object sender, RoutedEventArgs e)
{
    //Create a new picker
    FileOpenPicker filePicker = new FileOpenPicker();

    //Add filetype filters.  In this case wmv and mp4.
    filePicker.FileTypeFilter.Add(".wmv");
    filePicker.FileTypeFilter.Add(".mp4");

    //Set picker start location to the video library
    filePicker.SuggestedStartLocation = PickerLocationId.VideosLibrary;

    //Retrieve file from picker
    StorageFile file = await filePicker.PickSingleFileAsync();

    //If we got a file, load it into the media lement
    if (file != null)
    {
        mediaPlayerElement.Source = MediaSource.CreateFromStorageFile(file);
        mediaPlayerElement.MediaPlayer.Play();
    }
}

Once the video is loaded in the MediaPlayerElement, the user can simply press the casting button on the transport controls to launch a built-in dialog that allows them to choose a device to which the loaded media will be cast.

Note

Starting with Windows 10, version 1607, it is recommended that you use the MediaPlayer class to play media items. The MediaPlayerElement is a lightweight XAML control that is used to render the content of a MediaPlayer in a XAML page. The MediaElement control continues to be supported for backwards compatibility. For more information on using MediaPlayer and MediaPlayerElement to play media content, see Play audio and video with MediaPlayer. For information on using MediaSource and related APIs to work with media content, see Media items, playlists, and tracks.

Media casting with the CastingDevicePicker

A second way to cast media to a device is to use the CastingDevicePicker. To use this class, include the Windows.Media.Casting namespace in your project.

using Windows.Media.Casting;

Declare a member variable for the CastingDevicePicker object.

CastingDevicePicker castingPicker;

When you page is initialized, create a new instance of the casting picker and set the Filter to SupportsVideo property to indicate that the casting devices listed by the picker should support video. Register a handler for the CastingDeviceSelected event, which is raised when the user picks a device for casting.

//Initialize our picker object
castingPicker = new CastingDevicePicker();

//Set the picker to filter to video capable casting devices
castingPicker.Filter.SupportsVideo = true;

//Hook up device selected event
castingPicker.CastingDeviceSelected += CastingPicker_CastingDeviceSelected;

In your XAML file, add a button to allow the user to launch the picker.

<Button x:Name="castPickerButton" Content="Cast Button" Click="castPickerButton_Click"/>

In the Click event handler for the button, call TransformToVisual to get the transform of a UI element relative to another element. In this example, the transform is the position of the cast picker button relative to the visual root of the application window. Call the Show method of the CastingDevicePicker object to launch the casting picker dialog. Specify the location and dimensions of the cast picker button so that the system can make the dialog fly out from the button that the user pressed.

private void castPickerButton_Click(object sender, RoutedEventArgs e)
{
    //Retrieve the location of the casting button
    GeneralTransform transform = castPickerButton.TransformToVisual(Window.Current.Content as UIElement);
    Point pt = transform.TransformPoint(new Point(0, 0));

    //Show the picker above our casting button
    castingPicker.Show(new Rect(pt.X, pt.Y, castPickerButton.ActualWidth, castPickerButton.ActualHeight),
        Windows.UI.Popups.Placement.Above);
}

In the CastingDeviceSelected event handler, call the CreateCastingConnection method of the SelectedCastingDevice property of the event args, which represents the casting device selected by the user. Register handlers for the ErrorOccurred and StateChanged events. Finally, call RequestStartCastingAsync to begin casting, passing in the result to the MediaPlayerElement control's MediaPlayer object's GetAsCastingSource method to specify that the media to be cast is the content of the MediaPlayer associated with the MediaPlayerElement.

Note

The casting connection must be initiated on the UI thread. Since the CastingDeviceSelected is not called on the UI thread, you must place these calls inside a call to CoreDispatcher.RunAsync which causes them to be called on the UI thread.

private async void CastingPicker_CastingDeviceSelected(CastingDevicePicker sender, CastingDeviceSelectedEventArgs args)
{
    //Casting must occur from the UI thread.  This dispatches the casting calls to the UI thread.
    await Dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal, async () =>
    {
        //Create a casting conneciton from our selected casting device
        CastingConnection connection = args.SelectedCastingDevice.CreateCastingConnection();

        //Hook up the casting events
        connection.ErrorOccurred += Connection_ErrorOccurred;
        connection.StateChanged += Connection_StateChanged;

        //Cast the content loaded in the media element to the selected casting device
        await connection.RequestStartCastingAsync(mediaPlayerElement.MediaPlayer.GetAsCastingSource());
    });
}

In the ErrorOccurred and StateChanged event handlers, you should update your UI to inform the user of the current casting status. These events are discussed in detail in the following section on creating a custom casting device picker.

private async void Connection_StateChanged(CastingConnection sender, object args)
{
    await Dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal, () =>
    {
        ShowMessageToUser("Casting Connection State Changed: " + sender.State);
    });
}

private async void Connection_ErrorOccurred(CastingConnection sender, CastingConnectionErrorOccurredEventArgs args)
{
    await Dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal, () =>
    {
        ShowMessageToUser("Casting Connection State Changed: " + sender.State);
    });
}

Media casting with a custom device picker

The following section describes how to create your own casting device picker UI by enumerating the casting devices and initiating the connection from your code.

To enumerate the available casting devices, include the Windows.Devices.Enumeration namespace in your project.

using Windows.Devices.Enumeration;

Add the following controls to your XAML page to implement the rudimentary UI for this example:

• A button to start the device watcher that looks for available casting devices.
• A ProgressRing control to provide feedback to the user that casting enumeration is ongoing.
• A ListBox to list the discovered casting devices. Define an ItemTemplate for the control so that we can assign the casting device objects directly to the control and still display the FriendlyName property.
• A button to allow the user to disconnect the casting device.

<Button x:Name="startWatcherButton" Content="Watcher Button" Click="startWatcherButton_Click"/>
<ProgressRing x:Name="watcherProgressRing" IsActive="False"/>
<ListBox x:Name="castingDevicesListBox" MaxWidth="300" HorizontalAlignment="Left" SelectionChanged="castingDevicesListBox_SelectionChanged">
    <!--Listbox content is bound to the FriendlyName field of our casting devices-->
    <ListBox.ItemTemplate>
        <DataTemplate>
            <TextBlock Text="{Binding Path=FriendlyName}"/>
        </DataTemplate>
    </ListBox.ItemTemplate>
</ListBox>
<Button x:Name="disconnectButton" Content="Disconnect" Click="disconnectButton_Click" Visibility="Collapsed"/>

In your code behind, declare member variables for the DeviceWatcher and the CastingConnection.

DeviceWatcher deviceWatcher;
CastingConnection castingConnection;

In the Click handler for the startWatcherButton, first update the UI by disabling the button and making the progress ring active while device enumeration is ongoing. Clear the list box of casting devices.

Next, create a device watcher by calling DeviceInformation.CreateWatcher. This method can be used to watch for many different types of devices. Specify that you want to watch for devices that support video casting by using the device selector string returned by CastingDevice.GetDeviceSelector.

Finally, register event handlers for the Added, Removed, EnumerationCompleted, and Stopped events.

private void startWatcherButton_Click(object sender, RoutedEventArgs e)
{
    startWatcherButton.IsEnabled = false;
    watcherProgressRing.IsActive = true;

    castingDevicesListBox.Items.Clear();

    //Create our watcher and have it find casting devices capable of video casting
    deviceWatcher = DeviceInformation.CreateWatcher(CastingDevice.GetDeviceSelector(CastingPlaybackTypes.Video));

    //Register for watcher events
    deviceWatcher.Added += DeviceWatcher_Added;
    deviceWatcher.Removed += DeviceWatcher_Removed;
    deviceWatcher.EnumerationCompleted += DeviceWatcher_EnumerationCompleted;
    deviceWatcher.Stopped += DeviceWatcher_Stopped;

    //Start the watcher
    deviceWatcher.Start();
}

The Added event is raised when a new device is discovered by the watcher. In the handler for this event, create a new CastingDevice object by calling CastingDevice.FromIdAsync and passing in the ID of the discovered casting device, which is contained in the DeviceInformation object passed into the handler.

Add the CastingDevice to the casting device ListBox so that the user can select it. Because of the ItemTemplate defined in the XAML, the FriendlyName property will be used as the item text for in the list box. Because this event handler is not called on the UI thread, you must update the UI from within a call to CoreDispatcher.RunAsync.

private async void DeviceWatcher_Added(DeviceWatcher sender, DeviceInformation args)
{
    await Dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal, async () =>
    {
        //Add each discovered device to our listbox
        CastingDevice addedDevice = await CastingDevice.FromIdAsync(args.Id);
        castingDevicesListBox.Items.Add(addedDevice);
    });
}

The Removed event is raised when the watcher detects that a casting device is no longer present. Compare the ID property of the Added object passed into the handler to the ID of each Added in the list box's Items collection. If the ID matches, remove that object from the collection. Again, because the UI is being updated, this call must be made from within a RunAsync call.

private async void DeviceWatcher_Removed(DeviceWatcher sender, DeviceInformationUpdate args)
{
    await Dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal, () =>
    {
        foreach (CastingDevice currentDevice in castingDevicesListBox.Items)
        {
            if (currentDevice.Id == args.Id)
            {
                castingDevicesListBox.Items.Remove(currentDevice);
            }
        }
    });
}

The EnumerationCompleted event is raised when the watcher has finished detecting devices. In the handler for this event, update the UI to let the user know that device enumeration has completed and stop the device watcher by calling Stop.

private async void DeviceWatcher_EnumerationCompleted(DeviceWatcher sender, object args)
{
    await Dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal, () =>
    {
        //If enumeration completes, update UI and transition watcher to the stopped state
        ShowMessageToUser("Watcher completed enumeration of devices");
        deviceWatcher.Stop();
    });
}

The Stopped event is raised when the device watcher has finished stopping. In the handler for this event, stop the ProgressRing control and reenable the startWatcherButton so that the user can restart the device enumeration process.

private async void DeviceWatcher_Stopped(DeviceWatcher sender, object args)
{
    await Dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal, () =>
    {
        //Update UX when the watcher stops
        startWatcherButton.IsEnabled = true;
        watcherProgressRing.IsActive = false;
    });
}

When the user selects one of the casting devices from the list box, the SelectionChanged event is raised. It is within this handler that the casting connection will be created and casting will be started.

First, make sure the device watcher is stopped so that device enumeration doesn't interfere with media casting. Create a casting connection by calling CreateCastingConnection on the CastingDevice object selected by the user. Add event handlers for the StateChanged and ErrorOccurred events.

Start media casting by calling RequestStartCastingAsync, passing in the casting source returned by calling the MediaPlayer method GetAsCastingSource. Finally, make the disconnect button visible to allow the user to stop media casting.

private async void castingDevicesListBox_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
    if (castingDevicesListBox.SelectedItem != null)
    {
        //When a device is selected, first thing we do is stop the watcher so it's search doesn't conflict with streaming
        if (deviceWatcher.Status != DeviceWatcherStatus.Stopped)
        {
            deviceWatcher.Stop();
        }

        //Create a new casting connection to the device that's been selected
        castingConnection = ((CastingDevice)castingDevicesListBox.SelectedItem).CreateCastingConnection();

        //Register for events
        castingConnection.ErrorOccurred += Connection_ErrorOccurred;
        castingConnection.StateChanged += Connection_StateChanged;

        //Cast the loaded video to the selected casting device.
        await castingConnection.RequestStartCastingAsync(mediaPlayerElement.MediaPlayer.GetAsCastingSource());
        disconnectButton.Visibility = Visibility.Visible;
    }
}

In the state changed handler, the action you take depends on the new state of the casting connection:

• If the state is Connected or Rendering, make sure the ProgressRing control is inactive and the disconnect button is visible.
• If the state is Disconnected, unselect the current casting device in the list box, make the ProgressRing control inactive, and hide the disconnect button.
• If the state is Connecting, make the ProgressRing control active and hide the disconnect button.
• If the state is Disconnecting, make the ProgressRing control active and hide the disconnect button.

private async void Connection_StateChanged(CastingConnection sender, object args)
{
    await Dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal, () =>
    {
        //Update the UX based on the casting state
        if (sender.State == CastingConnectionState.Connected || sender.State == CastingConnectionState.Rendering)
        {
            disconnectButton.Visibility = Visibility.Visible;
            watcherProgressRing.IsActive = false;
        }
        else if (sender.State == CastingConnectionState.Disconnected)
        {
            disconnectButton.Visibility = Visibility.Collapsed;
            castingDevicesListBox.SelectedItem = null;
            watcherProgressRing.IsActive = false;
        }
        else if (sender.State == CastingConnectionState.Connecting)
        {
            disconnectButton.Visibility = Visibility.Collapsed;
            ShowMessageToUser("Connecting");
            watcherProgressRing.IsActive = true;
        }
        else
        {
            //Disconnecting is the remaining state
            disconnectButton.Visibility = Visibility.Collapsed;
            watcherProgressRing.IsActive = true;
        }
    });
}

In the handler for the ErrorOccurred event, update your UI to let the user know that a casting error occurred and unselect the current CastingDevice object in the list box.

private async void Connection_ErrorOccurred(CastingConnection sender, CastingConnectionErrorOccurredEventArgs args)
{
    await Dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal, () =>
    {
        //Clear the selection in the listbox on an error
        ShowMessageToUser("Casting Error: " + args.Message);
        castingDevicesListBox.SelectedItem = null;
    });
}

Finally, implement the handler for the disconnect button. Stop media casting and disconnect from the casting device by calling the CastingConnection object's DisconnectAsync method. This call must be dispatched to the UI thread by calling CoreDispatcher.RunAsync.

private async void disconnectButton_Click(object sender, RoutedEventArgs e)
{
    if (castingConnection != null)
    {
        //When disconnect is clicked, the casting conneciton is disconnected.  The video should return locally to the media element.
        await castingConnection.DisconnectAsync();
    }
}