Windows Phone 7 Development : Working with Video (part 2) - Coding the Application

3/18/2011 9:30:13 AM

3. Coding the Application

In Solution Explorer, open MainPage.xaml.cs and replace the code you find there with the following C# code blocks that will implement the media player's functions.

3.1. Specifying the Namespaces

Begin by listing the namespaces the application will use. Notice the inclusion of Microsoft.Phone.Tasks that will allow us to launch Windows Phone's default media player. As for the MediaElement, it is declared in the XAML page, which you will simply reference here by the control's name.

using System;
using System.Windows;
using System.Windows.Media;
using Microsoft.Phone.Controls;
using Microsoft.Phone.Tasks;

namespace MediaPlayerDemo
public partial class MainPage : PhoneApplicationPage

3.2. Initializing Variables

The variable _updatingMediaTimeline is an extremely important variable that stops the infinite loop in this demo. By setting _updatingMediaTimeline to true while the media timeline (Slider control) is being updated during the CompositionTarget.Rendering event, the media's backward and forward event will wait to be processed until the timeline update is completed. Another way to look at this complexity is to see the purpose of the Slider control that is responsible for displaying the timeline of the media being played. But the Slider control is also responsible for allowing the user to interact to drag the slider forward or backward in order to move the media position. _updatingMediaTimeline will allow only one specific behavior to happen in the Slider control, thereby avoiding unwanted application behavior.

private bool _updatingMediaTimeline;

public MainPage()

_updatingMediaTimeline = false;

// rewinds the media player to the beginning
mediaPlayer.Position = System.TimeSpan.FromSeconds(0);

3.3. Handling Video Download Progress

As the video file download progresses, you will be receiving the percentage of the file got downloaded and you will be displaying the progress updates back to the user by updating the lblDownload.

// Download indicator
mediaPlayer.DownloadProgressChanged += (s, e) =>
lblDownload.Text = string.Format("Downloading {0:0.0%}",

3.4. Handling Video Buffering

You will be setting video BufferingTime property and as the video buffering time progresses you will receive a callback where you will update lblBuffering.

// Handle media buffering
mediaPlayer.BufferingTime =
mediaPlayer.BufferingProgressChanged += (s, e) =>
lblBuffering.Text = string.Format("Buffering {0:0.0%}",

3.5. Showing Time Elapsed in the Media Player

CompositionTarget.Rendering is a frame-based event that will fire once per frame, allowing you to update the media timeline (Slider control) that reflects how much of the media is played. By default the event will fire 60 times in one second. You can check this by checking the value of Application.Current.Host.Settings.MaxFrameRate. By using the CompositionTarget.Rendering event, you will be able to see the smooth media player timeline filling up as the media plays.

// Updates the media time line (slider control) with total time played
// and updates the status with the time played
CompositionTarget.Rendering += (s, e) =>
_updatingMediaTimeline = true;
TimeSpan duration = mediaPlayer.NaturalDuration.TimeSpan;
if (duration.TotalSeconds != 0)
double percentComplete =
mediaPlayer.Position.TotalSeconds / duration.TotalSeconds;
mediaTimeline.Value = percentComplete;
TimeSpan mediaTime = mediaPlayer.Position;
string text = string.Format("{0:00}:{1:00}",
(mediaTime.Hours * 60) + mediaTime.Minutes, mediaTime.Seconds);

if (lblStatus.Text != text)

lblStatus.Text = text;

_updatingMediaTimeline = false;

When defining the event handler of CompositionTarget.Rendering, you can use the lambda expression to create a delegate that contains the programming logic. For example, you can rewrite CompositionTarget.Rendering += (s, e) => { ... } by first declaring the event handler CompositionTarget.Rendering += new EventHandler(CompositionTarget_Rendering) and then creating a method void CompositionTarget_Rendering(object sender, EventArgs e) { ... }. Using the lambda expression technique makes the code much more readable and in this demo project gives you the ability to group the relevant code together. For more information on the lambda expression, please refer to

3.6. Implementing the Pause Button

When the Pause button is clicked, invoke MediaElement.Pause to pause the media player. Notice also here that you are updating the Status label, communicating to the user the media is in pause mode. Also notice that for unknown reasons, the media player might not be able to pause. You can use mediaPlayer.CanPause to make sure you can pause and otherwise set the Status label to warn the user it could not pause.

private void btnPause_Click(object sender, RoutedEventArgs e)
if (mediaPlayer.CanPause)
lblStatus.Text = "Paused";
lblStatus.Text = "Can not be Paused. Please try again!";

3.7. Implementing the Stop Button

When the stop button is clicked, invoke MediaElement.Stop to stop the media player and then rewind the media player back to the beginning and update the Status label as "Stopped."

private void btnStop_Click(object sender, RoutedEventArgs e)

mediaPlayer.Position = System.TimeSpan.FromSeconds(0);
lblStatus.Text = "Stopped";

3.8. Implementing the Play Button

When the play button is clicked, invoke MediaElement.Play to play the media player.

private void btnPlay_Click(object sender, RoutedEventArgs e)

3.9. Implementing the Mute Button

When the Mute button is clicked, set MediaElement.IsMuted to true in order to mute the sound or set it to false to turn on the sound.

private void btnMute_Click(object sender, RoutedEventArgs e)
if (lblSoundStatus.Text.Equals("Sound On", StringComparison.CurrentCultureIgnoreCase))
lblSoundStatus.Text = "Sound Off";
mediaPlayer.IsMuted = true;
lblSoundStatus.Text = "Sound On";
mediaPlayer.IsMuted = false;



To mute the player, you could have set MediaElement.Volume to zero instead of setting the IsMuted property to true, as we did in our example.

3.10. Implementing Seek

When the Slider control that displays the timeline of the media is clicked or dragged, MediaElement.Position moves either forward or backward, depending on the user's input on the Slider control. See Figure 15-3 for dragging the slider to the right in order to move forward in the video timeline.

private void mediaTimeline_ValueChanged(object sender,
RoutedPropertyChangedEventArgs<double> e)

if (!_updatingMediaTimeline && mediaPlayer.CanSeek)
TimeSpan duration = mediaPlayer.NaturalDuration.TimeSpan;
int newPosition = (int)(duration.TotalSeconds * mediaTimeline.Value);
mediaPlayer.Position = new TimeSpan(0, 0, newPosition);

Figure 3. Dragging the slider to skip the video


Using MediaElement.Position you can jump to any part of the media.

3.11. Implementing the MediaPlayerLauncher

When the MediaPlayerLauncher button is clicked, invoke the MediaPlayerLauncher task to launch the default Windows Phone media player.

private void btnMediaPlayerLauncher_Click(object sender, RoutedEventArgs e)
MediaPlayerLauncher player = new MediaPlayerLauncher();
player.Media = new
//player.Media =
// new Uri("ARCastMDISilverlightGridComputing_ch9.wmv",
// UriKind.Relative);
//player.Location = MediaLocationType.Data;


Notice the commented code where MediaPlayerLauncher is going to play the content that is part of the application. player.Location is set to MediaLocationType.Data, which means that it will look at the isolated storage for the file named ARCastMDISilverlightGridComputing_ch9.wmv. If you set player.Location to MediaLocationType.Install, the media file must be added to the application as the content and also the media source's Uri must have UriKind.Relative, which basically means the file is part of the application. The only problem with this is that the size of the application install will get much bigger.

3.12. Testing the Finished Application

To test the application, press F5. The result should resemble Figure 1. Try clicking each button: Play, Pause, Stop, and Mute. Also, as the movie plays, take note of the buffering and downloading progress status. You can also drag the slider back and forth to skip around the movie scenes. You can also put your own favorite movie link if you know of any.

In this first demo, you learned to create a custom media player and then learned to launch the default Windows Phone media player. Both MediaElement and MediaPlayerLauncher accessed the video content on the Web because typically video files are very big. But if you are adding simple sound effects to an application, it is not always ideal to download the contents from the Web when you can simply package the sound along with the application. This is especially true if you are planning to create a game where all the graphical and media assets are packaged as the part of the application. In the next demo, you will learn to add sound effects to an application.

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