Usage of the audio element consists of adding one or more audio sources
and setting some options.
Use the method setAlternativeContent() to show alternative
content if the audio cannot be played. The alternative content can be any
widget; you can set it to an alternative media player (QuickTime, Flash,
...), show a Flash movie, an animated gif, a text, a poster image, ... .
There are two reasons why the browser may use the alternative content:
either because the browser does not support the HTML5 audio tag
because none of the specified sources contain an audio format that is
The addSource() and setAlternativeContent() may not be
called after the widget is rendered.