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4. Video On Demand

4.1 Overview

What is Video On Demand ?

With Video On Demand (VOD), the client can start the video when he wants, make pauses, go forward and go back in the video. It's of course the best of video streaming and the dream for every client.

Hardware required

But VOD is a very big consumer of resources for the server and the network. VOD is unicast, not multicast. This mean that if 50 clients are doing VOD with the same server, watching a 5 Mbit/s MPEG 2 video, the resources needed as a minimum are the following :

• for the VOD server : 5*50=250 Mbit/s disk access and a 250 Mbit/s connection to the backbone,
• for the Backbone : 250 Mbit/s bandwidth,
• for the client : 5 Mbit/s connection to the backbone.

You can see that VOD needs huge resources for the server in term of disk access and network connection, and for the backbone.

Design of the VOD solution

The design 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 we use to seek in the video.

On the VOD server, you need to install a Web server. For example, we use a Linux server running Apache as HTTP daemon. But other O.S. and other Web server should work too, but we have never tested. Make your MPEG 1 or 2 files available to the clients on the Web server.

On the client, you only need vlc installed.

4.2 VOD with VideoLAN

On the server

For example, we have a Web server whose DNS name is vod.videolan.org. On this server, there are two MPEG files video1.mpg and video2.mpg available to the clients at the adresses http://vod.videolan.org/test/video1.mpg and http://vod.videolan.org/test/video2.mpg.

On the client

On the client, run vlc with this command line to view the first video :

% vlc http://vod.videolan.org/test/video1.mpg

% vlc http://vod.videolan.org/test/video2.mpg

You can also use the interface : click on "Net" and select HTTP and enter the URL "vod.videolan.org/test/video1.mpg" or "vod.videolan.org/test/video2.mpg".

Client launched by a Web browser

The idea is to have a Web page with the list of the videos available, and, when you clic on a video, vlc starts to display it.

You have to write the Web page with regular hypertext links to the video files and configure you Web browser to launch vlc when a file with ".mpg" (and ".mpeg" and ".vob") extension is selected. Tell the client that vlc accepts the URL as a command line : with this configuration, the file will not be stored on the client's hard drive but will be directly read by vlc.

Using a channel tool for VOD

You can use miniVLCS and enable the clients to select channel 1 to view the first video, channel 2 to view the second video, and so on.

Install miniVLCS on a Linux machine (it can be the same machine as the VOD server). Please, refer to the section describing the building of miniVLCS.

In the following example, the configuration file vlcs.conf should look like that :

I: nostream
http://vod.videolan.org/test/video1.mpg
http://vod.videolan.org/test/video2.mpg

Then run miniVLCS as a normal user :

% ./vlcs

The simplest solution is to use the interface of vlc : click on "Net", select "Channel server", write its IP address or DNS name.

Then, you see a new section "Network Channel" on the interface.

Select "1" and click on "Go!" to view the first video. Select "2" and click on "Go!" to view the second video.

This function is broken in release 0.4.0 of vlc.

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