Video Compression: An MPEG Story

Requirements From Any Compression Algorithm
(Just What I Needed)

Any compression algorithm should satisfy the following requirements, if we have to standardize the compression-uncompression procedure:

It should have a high compression rate at the same time maintain a good enough quality so that uncompressed file is not so much different from the original file and contains almost all of the important information
The technique of compression should be simple, in fact the least complex technique is preferred
The delay introduced in compression should be very small
Based on application requirements, there are two kinds of codecs - symmetric and asymmetric. Symmetric algorithms take the same amount of time to compress and uncompress files, while asymmetric codecs spend more time in one of the above processes. Asymmetric codecs are usually preferred, because the general user would like to compress the file once, and then uncompress it whenever needed, so that we need the decompression time to be small while the compression time can be allowed to be big because we are only going to compress the file once. This mode of the codec is called the retrieval mode, and it is usually expected to have the following properties:

FFWD, REW should be possible with simultaneous display of the movie
Random access with speeds should be less than 0.5 s
The format should be independent of frame size and framerate, and should support several rates - this means that users who are trying to stream movie previews, for example, should be able to choose between slow and high bandwidth connections, so that the website can provide to both slow and fast connections. For example, check out this site for different speeds at which you can view the preview for the 2000 film, High Fidelity.
The audio and video tracks should be in sync. Nowadays there are programs which can fix audio-video sync, and are easily available over the internet. For example, try www.vcdhelp.com

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