mpeg movie file formats

A plethora of file formats can be used on the web. For example, ASCII text files, images files, sound files, and movie files. Sometimes files can be converted between different formats. Image files and movie files are the main files that must be considered, carefully before being included in a company web page. As those files are large, it takes alot of time to download large files over the net. This could be malign for a business institution hoping to conduct transactions via the web. It is necessary to briefly analyses these formats as to infer their features.

MPEG

MPEG or Motion Picture Experts Group is an ISO (International Standards Organisation) standard file format for displaying motion picture files.

MPEG Compression

The compression method is efficient. This is because MPEG exploits the redundancy between movie frames. This is called interframe compression. The compression depends on the movie frames, and depending on them different but related frame compression can be used.

• I frame intraframe compression - Here the pictures are coded independant of any other picture, and considers only the redundant information pertaining to the current. For example, if a section of a video picture or frame shows an object that is of just one colour, then every pixel corresponding to that object need not fully specify that colour. Thus, this section could be defined as containing colour x, and not specify colour x for each of the objects pixels many times over.
• P and B frame interframe compression Here, if picture x has an object in it that is in the exact same position in frame x+1, then the information for that object need not be transmitted in its entiriety for both frames. This process is sometimes referred to as bidirectional prediction.

Advantages

1. Platform independance Many graphics and video cards from manufacturers support MPEG playback. Even Windows 95 and NT support MPEG playback from within the OS.
2. Device independance Several vendors manufacture MPEG encoding solutions. This drives down prices and ensures continued supply of encoders.
3. Quality MPEG - compressed video is the highest quality available at bit rates below 200 Kb/s.

Disdvantages

1. Needs alot more computation than JPEG, especially with B pictures.
2. Editing MPEG frames is a problem due to interframe compression. This disadvantage has enabled other methods like M-JPEG to become popular for video files.
3. Sometimes JPEG could be used to represent movie files, provided, the pictures do not change faster than 30 frames/s. This is called M-JPEG. In this case MPEG would be of no use.

As usual, this all depends on the extent of the functions to be served by the web page. A company wanting to use web pages for marketing its products and services needs to carefully organise the web page so that it encourages net-surfers. The users would not be impressed if the web page consists of large image files that keeping them waiting indefintely. Sometimes web surferers would be using a text-only browser like Lynx. Therefore, it is essential to cater for the needs of every user. High resolution pictures call for JPEG, but not all users will poesses a high quality sound card and monitor. Having separate web pages to cater for different users might be a good start.