SL12: Pausing, Stopping, or Playing Media in Silverlight MediaElements

Important Information about Techniques

See Understanding Techniques for WCAG Success Criteria for important information about the usage of these informative techniques and how they relate to the normative WCAG 2.0 success criteria. The Applicability section explains the scope of the technique, and the presence of techniques for a specific technology does not imply that the technology can be used in all situations to create content that meets WCAG 2.0.

Description

The objective of this technique is to create a control user interface for the Silverlight MediaElement object. The controls enable users to pause or stop the video to prevent the video images on the MediaElement surface from moving, and stop video-associated audio. These UI controls enable an interaction defined in code event handlers. Each handler calls one of the following MediaElement methods:

Note that by default, a MediaElement will start playing its media as soon as the UI loads completely AND the media source file is downloaded (or a certain buffer size is reached, in the case of streaming media). Use the AutoPlay property to change this default.

Examples

Example 1: Providing MediaElement controls in the UI

This example has a UI definition in XAML and interaction logic in C#.

<UserControl x:Class="MediaElementControls.MainPage"
  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
 >
  <Grid x:Name="LayoutRoot">
      <StackPanel>
          <MediaElement x:Name="media" Source="/xbox.wmv"
         Width="300" Height="300" 
         AutomationProperties.Name="Video of new Fable game for XBox"           
      />
          <Grid Name="UIControls">
              <Grid.ColumnDefinitions>
                  <ColumnDefinition Width="*" />
                  <ColumnDefinition Width="*" />
                  <ColumnDefinition Width="*"/>
              </Grid.ColumnDefinitions>
              <Grid.RowDefinitions>
                  <RowDefinition Height="*" />
                  <RowDefinition Height="Auto" />
                  <RowDefinition Height="20" />
              </Grid.RowDefinitions>
              <Button Click="StopMedia" 
   Grid.Column="0" Grid.Row="1" Content="Stop" />
              <Button Click="PauseMedia" 
   Grid.Column="1" Grid.Row="1" Content="Pause" />
              <Button Click="PlayMedia" 
   Grid.Column="2" Grid.Row="1" Content="Play" />
              <Button Click="MuteMedia" 
  Grid.Row="2" Grid.Column="0" Content="Mute" />
              <TextBlock Name="VolumeLabel" Grid.Row="2" Grid.Column="1" HorizontalAlignment="Right">Volume</TextBlock>
              <Slider Height="20"
          Value="{Binding Volume, Mode=TwoWay, ElementName=media}"
          Minimum="0" Maximum="1"
          Grid.Row="2" Grid.Column="2" Grid.ColumnSpan="2"
              AutomationProperties.LabeledBy="{Binding ElementName=VolumeLabel}"/>
          </Grid>
      </StackPanel>
  </Grid>
</UserControl>

private void StopMedia(object sender, RoutedEventArgs e)
{
    media.Stop();
}
private void PauseMedia(object sender, RoutedEventArgs e)
{
    media.Pause();
}
private void PlayMedia(object sender, RoutedEventArgs e)
{
    media.Play();
}
private void MuteMedia(object sender, RoutedEventArgs e)
{
    Button target = sender as Button;
    // mute if not muted, unmute if already muted, in either case make sure the button content for text and accessibility info is updated
    if (!media.IsMuted)
    {
        media.IsMuted = true;
        target.Content = "Unmute";
    }
    else
    {
         media.IsMuted = false;
         target.Content = "Mute";
     }
}

This example is shown in operation in the working example of Media Element Controls.

Resources

Resources are for information purposes only, no endorsement implied.

Audio and Video Overview
MediaElement Class
Silverlight Media Framework - a framework and a media player control implementation that incorporates many of the Silverlight techniques related to MediaElement

Related Techniques

Tests

Procedure

Using a browser that supports Silverlight, open an HTML page that references a Silverlight application through an object tag. The application is expected to incorporate a MediaElement in the user interface.
Check that interactive controls are available so that users can pause or stop the media.
Check that when activated, the controls stop or pause the media.

Expected Results

#2 and #3 are true.

If this is a sufficient technique for a success criterion, failing this test procedure does not necessarily mean that the success criterion has not been satisfied in some other way, only that this technique has not been successfully implemented and can not be used to claim conformance.