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<chapter id="vod"><title id="tvod">Video On Demand</title>

<sect1><title>Overview</title>

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<para>With Video On Demand (VOD), the user can start the video when he
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wants, make pauses, go forward and back in the video. It is of course
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the best in video streaming and the dream for every user.</para>

<para>VOD is a very big consumer of resources for the server and the
network. VOD is unicast, not multicast : this means that the network
and server resources needed are directly proportional to the number of
clients.</para>

<para>The design of VideoLAN's VOD solution is very simple. The idea
is to do HTTP streaming, i.e. stream an MPEG video encapsulated in
HTTP. The regulation of the bitrate between the client and the server
is done automatically by TCP. With HTTP version 1.1, there is the
possibility to seek in a file downloaded, that's what we use to seek in
the video.</para>
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<sect1><title>On the server side</title>

<para> On the VOD server, you need a running Web server. For example,
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you can use a Linux server running Apache. Other operating systems
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and other Web servers should work too, but we have never tested.</para>

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<para>Make your MPEG-1, MPEG-2 or MPEG-4 / DivX files available to the
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clients on the Web server. </para>

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<para>For example, we have a Web server whose DNS name
is <emphasis>localserver</emphasis>. On this server,
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we put an MPEG file <filename>video1.mpg</filename>
which will be available to the clients at the URL
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<filename>http://localserver/test/video1.mpg</filename>.</para>
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<sect1><title>On the client side</title>

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<screen>
<prompt>% </prompt><userinput>vlc -vvv http://localserver/test/video1.mpg</userinput>
</screen>
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<para>VLC starts to read the stream nearly immediately and you can
seek in the stream, make pauses, etc... as if the stream was a local
file.</para>