Video Streaming Basics
There are two basic types of video streaming – live webcasts and video on demand (VOD). Webcasts present technological challenges that make them impractical for most purposes, but VOD is fairly easy to set up for the average webmaster.
For VOD the video material is stored on a server so that it is available for viewing at any time. The proper type of video file must be used so the first step is to edit the video material and save it in the appropriate format.
Most professional video editing software has the ability to save the file in a streaming format, and there is usually a choice of video sizes and bit rates to suit a variety of connection speeds. The most common video streaming formats are Real Media, Apple Quicktime and Windows Media.
Streaming formats are compressed, which means that part of the original video is discarded to make for a smaller file size and faster transmission speeds. There are many video compression schemes but the most common way to compress video is to take parts of the video image which don't change (such as the background) and repeat the information (rather than the image itself) from frame to frame.
This means that video images which are not 'busy' will compress more and give better results for streaming. Talking heads are ideal for streaming video, but action-packed scenes have too much visual information.
Other things being equal large video files offer better image quality but have the disadvantage of requiring fast Internet connections. Small video files can be viewed with dialup connections but lose out in terms of image quality.
Bit rate is the rate of data transmission and can range from 56,000 bits per second for dialup to millions of bits per second for cable connections. Given this range, how can you provide streaming video that will satisfy all of your viewers? If the video file is too large your dialup viewers will not be able to watch it. If the video is small enough to be viewed with a dialup connection the quality will be too poor to satisfy your broadband viewers.
The simple answer is to provide several versions of the same video. There should be (at least) 3 different versions – a large file for fast connections, a medium sized file for average connections and a small file for dialup connections. Viewers simply select which file to view according to their connection speed.
Your video files (like your other web site files) must be stored on a computer called a server. These are specialized computers that wait for incoming requests and 'serve' the material requested.
Video files can be stored on specialized streaming servers or they can be hosted on a regular HTTP server. HTTP servers are used for delivering the text and images that make up the average web page, but are unsuitable for handling a large number of requests for streaming video.
A low traffic website may be able to host a video file on a HTTP server, but web sites which receive significant traffic with frequent requests for video files should use a video streaming server to host the video content. Besides being able to handle a large number of requests, streaming servers also have the advantage of being able to detect connection speeds and deliver the appropriate video content automatically.
