RealPlayer™
Plug-in
A RealPlayer object may be embedded into a Web page
to enhance the page with streaming audio and video. RealPlayer can also be
delivered as a browser plug-in on multiple plat forms.
Figure 33.14 demonstrates streaming audio in a Web page by embedding a
Real-Player object in the page using embed element.
Users can select from several different audio sources; this selection then
calls a JavaScript which invokes RealPlayer methods to play the selected audio
stream.
<?xml
version = "1.0"?>
<!DOCTYPE
html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<!--
Fig. 33.14: real.html -->
<!--
Embedding RealPlayer into an XHTML page -->
<html
xmlns = "http://www.w3.org/1999/xhtml">
<head>
<title>Live
Audio!</title>
<script
type = "text/javascript">
<!--
var
locations =
[
"http://www.cnn.com/video/audio/cnn.ram",
"http://www.real.com/showcase/kingredir.ram",
"http://radio.onlinemusic.com/play/"
+
"jazzsummit.com/rm"
]
function
change( loc )
{
raControl.SetSource(
locations[ loc ] );
raControl.DoPlayPause();
}
//
-->
</script>
</head>
<body>
<p>Pick
from my favorite audio streams:
<select
id = "streamSelect" onchange =
"change(
this.value )">
<option
value = "">Select a station</option>
<option
value = "0">CNN</option>
<option
value = "1">KING-FM</option>
<option
value = "2">Jazz Summit</option>
</select></p>
<br
/>
<embed
id = "raControl" src = ""
type
= "audio/x-pn-realaudio-plugin" width = "275"
height
= "125" controls = "Default"
autostart
= "false" />
</body>
</html>
Fig. 33.14 Embedding RealPlayer in a Web page
The embed element
in lines 42–45 embeds the RealPlayer plug-in into the page. The type
attribute
specifies the MIME type of the
embedded file, which in this case is the MIME type for streaming audio. (Remember that MIME is a standard for
specifying the format of content so the browser can determine how to handle the
content.) The width and height
attributes
specify the dimensions of the
space the control occupies on the page. The autostart attribute determines whether the audio
starts playing when the page loads (for this example, we set it to false). The controls attribute specifies which
controls users can access (e.g., Play
button, Pause button and Volume Control). Setting controls to Default places the standard control buttons on screen. A list of the avail-able
controls can be found at the site
www.real.com/devzone/library/stream/plugtest/plugin.html
We do not set the src attribute of the embed element.
Normally, this is the location of the streaming audio, but in this example, we
use JavaScript to change the source dynamically based on user selections.
Now that the player is embedded
in the Web page, we use scripting to activate the streaming audio. The select menu
(line 33) lists three radio stations, corresponding to the three entries in the
array locations (defined at line 14), which contain the actual URLs for the live audio
of those stations. When the selection changes, function change (line
20) is called by the onchange event. This function calls methods SetSource and DoPlayPause of the
RealPlayer object. Method SetSource sets the source URL of the audio
stream to be played. Then, method DoPlayPause toggles between pausing and playing the stream. [Note: In this case, the stream is paused because it has not started
playing yet, so it begins playing in response to the call to DoPlayPause.]
In this example, we only explore
streaming audio. The latest versions of RealPlayer support streaming video as
well. To view streaming video with RealPlayer, visit the fol-lowing sites:
www.cnn.com
www.msnbc.com
www.broadcast.com/television
To learn more about programming with RealPlayer,
visit the RealPlayer DevZone at
www.realnetworks.com/devzone/index.html
A few years, ago broadcasting
personal streaming audio and video required a dedicated server and expensive
software. Today, open source software, such as Darwin Streaming Server and RealNetwork’s Basic Server G2, provide “home-made” servers, such as Linux or
Apache running on a PC, with streaming capability. These applications are
available free for download from www.shareware.com. With limited server processor power and Internet bandwidth, this type
of set-up cannot support the same number of streams and bit-rates as a
dedicated streaming server.
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