Surfing The World Wide Waves, a weekly article
Video Compression and the World Wide Web
Bandwidth is one of the most limiting factors for the progression of video on the World Wide Web but over the past two or three years great advances have taken place through the development of MPEG-4 and now MPEG-8 compression. These compression/decompression (codecs) allow people to stream video in a far more efficient way.
For a moment there was a huge row about Napster and it's effect on the music industry, claiming that through making high quality copies of music available so easily online this would kill the industry. Bandwidth has not been great enough for video to be streamed online until now with the arival of ADSL and broadband connections.
How does compression work?
Video in it's most basic form is a series of images which appear at a rate of 25 frames per second for pal and 29.9 frames per second for NTSC. Each individual frame takes up a certain amount of bandwidth so through reducing the colour depth it is possible to reduce the amount of data sent for each image. As an addition to this it is possible to make the image smaller to further reduce the amount of data which must be sent. With the MPEG formats such as MPEG 2 the codec goes one step further so that although the video is continuing at the same rate one image will be complete whilst the other will only show the portions which have changed. In so doing we have what is refered to as a key frame followed by several frames with only what has changed as data. Imagine for example the term World Wide Web. If we decide to shorten it to WWW then we know that it is the same thing but the information is contained within a much smaller amount of space. As each MPEG generation progresses more efficient methods of compression are developed helping reduce the bandwidth to show clear video.
With a 56k modem video is no more than a small thumbnail which changes every few seconds to reveal another image whilst the sound plays quite well. At ISDN level the image is fluid and motion can be seen quite clearly although the image is limited to some degree. With MPEG-8 and Windows Media player 9 amongst other softwares it is easier to send a one minute clip with smooth motion and high enough quality to be played full screen. An example of this would be my video of the lake parade which can be played full screen with no visible loss of quality.
Video Compression through Premiere
Video compression is becoming a more and more important part of working with the moving image. This is shown through the strategy of companies such as Adobe Premiere which includes the compression software to compress Windows media files. You may also install the real media plug in which allows you to encode real media files. In so doing rather than invest thousands in various softwares everything is centralized making it much easier for users to create and output their product at a very affordable price.