IEC: On-Line Education: WPF: Desktop Streaming Media Production

Once users have created, enhanced, and encoded the streaming media and created the HTML page that will contain the media player and related data, they must post the files on the appropriate Web servers. At this point, the Internet service provider (ISP) must be contacted to gather some information. The following information is required:

a log-on identification number and password for the Internet servers to which the pages and media will be posted
the address for the HTML server where the layout and redirector files will be stored on the Web server; this is the directory path that will be used to transfer the files with a file transfer protocol (FTP) program
the address for the Windows Media or RealNetworks server where the .asf, .wma, or .rm file (the streaming media) will be stored on the Web server; this is the directory path that will be used to transfer the file with an FTP program

Before the files are uploaded, one more file (called a redirector or pointer file) must be created. To understand the need for this file, an examination of the streaming-media process is required (see Figure 1).

Figure 1. The Streaming-Media Process

There are two servers involved in the process. One serves the HTML pages, and another serves the streaming media. The word server here may refer to separate hardware devices (i.e., a physical computer) or two software servers running on the same computer. One reason for this is that the servers use different protocols to transfer the data. The Web pages travel via hypertext transfer protocol (HTTP). This protocol makes use of error checking to ensure more effectively that the page and all of its parts are delivered to the requesting client. This error checking, while making delivery more reliable, slows the file-transfer process. Because of the greater need for speed, many streaming multimedia programs use a faster protocol called user datagram protocol (UDP). UDP is faster because it does not incorporate error checking.

The client will send a request for the streaming media to the HTML server, and the HTML server will redirect the request to the media server. It does this via the redirector or pointer file. This file is usually placed in the same folder as the HTML page. An example of a typical redirector file is as follows:



<ASX version = "3.0">
<Entry>
<Ref href = "mms://mediaserver/folder/filename.asf" />
</Entry>
</ASX>

In the above example, the client request is redirected to the Microsoft Media server to stream the media files.



rtsp://sampleserver/mediafolder/filename.rm

In the above example, the client request is redirected to the RealServer.

8. The Final Step >>