Format of Video DVD

Although the capacity of storage in the DVD is great, the not compressed data of video of a film, never could fit in a DVD. In order to be able to insert a film in a DVD, a compressor makes lack of video. A called group MPEG (Moving Picture Experts Group), establishes the standards to compress the films in digital format. When the films are put in the DVDs, they are codified in stored format MPEG-2 and next in the disc. The compression format widely is accepted like an international standard. Your reproducer DVD contains a coder MPEG-2, who can decompress these data as fast as your you can see the film.
Reduction as large as the data
A film normally is filmed to an average of 24 plots per second. This means that every second, are 24 complete images in the screen. The Japanese American televisions use a called format NTSC, which unfolds a total of 30 plots per second, although it does in a sequence of 60 fields, containing each alternative lines of the image. Other countries, like Spain, use the format the PAL, that unfolds 50 fields per second, but with a greater resolution. When existing this difference between averages of plots and resolution, a film MPEG needs to be formatted for a system or another one, (NTSC or the PAL).
The coder MPEG who creates the compressed film, analyzes each plot and decides like codifying it. The compression uses a little the same technology that uses the compressors of digital photographies to eliminate duplicated or irrelevant data. Also it uses information of other plots to reduce the complete size of the file. Each plot can be codified in one of the three following ways:

• Like one intraframe, which contains a complete image of the data for that plot. This method to codify provides with the smaller compression.
• One “predicted frame”, which contains sufficient information to say to him to reproducer DVD as to show to the plot based on infraframe or predicted frames more recent.
• Bidirectional. In order to show this type of plot, the reproducer must have the information of infraframe or predicting adjacent. The USA the interpolation to calculate the position and color of each pixel.
  

Following the type of scene, the coder will decide that type of plots to use. For example, if there is a scene of very fast action that must be turned, where the things change from a plot to another one quickly, many infraframes will have more to be codified. All this can sound something complicated, but already you will have realized to amount of work that needs to make your reproducer DVD to decode a film MPEG-2. A great amount is needed processing and also codecs necessary to make work it.