Heres a quick guide to help you understand MPEG, the standardization format, and thereby have a better picture of the technical aspects behind the various video and audio files you encounter.
First of all, MPEG stands for Motion Picture Experts Group. The group was established by the ISO/IEC(International Organization for Standardization and International Electrotechnical Commission) in 1988. It has been responsible for producing 5 of the basic standardized formats out there. MPEG TYPES DEFINED
MPEG-1: VCD(video CD) and MP3.
MPEG-2: DVD and Digital Television set top boxes.
MPEG-4: Multimedia for fixed and mobile web devices.
MPEG-7: Multimedia content description standard. It uses XML to store metadata, and can be attached to timecode.
MPEG-21: "Rights Expression Language," means of sharing digital rights/permissions/restrictions for digital content from content creator to content consumer. HOW MPEG WORKS For the advanced technophile.
The MPEG codecs use lossy data compression using transform codecs. As of 2005, in a typical/widely-used lossy transform codec, samples of picture or sound are taken, chopped into small segments, transformed into a frequency space, and quantized. The resulting quantized values are then entropy coded.
This typical model is extended by moving picture coding systems such as MPEG-1, MPEG-2, and MPEG-4. In particular, an extra step is added, where the picture content is predicted from past reconstructed images before coding, and only the differences from the reconstructed pictures, and any extra information needed to perform the prediction, are coded.
MPEG standardizes only the bitstream format and how a decoder should interpret such a bitstream. The encoding methods themselves (and many details about decoders), are not standardized in any way, although there are reference implementations available that produce valid bitstreams for testing. The goal of this standardization approach is that any decoder should be able to decode material produced by any encoder that follows the same standard, regardless of which particular encoder (or which company's encoder) produced the encoded material. |
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