MAGIX Video Easy 3 HD, Руководство пользователя

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Annex: Digital Video and Data Storage 77
Annex: Digital Video and Data Storage
MPEG Compression
MPEG means "Moving Picture Experts Group" and defines a workgroup which
cooperates with the International Standards Organization (ISO) as well as the
international Electro Technical Commission (ETC) to develop standards for
video and audio coding.
Generally, the graphic data rate of the digital video standard is 167 megabits
per second, which, when not compressed, requires a far higher storage
capacity than a DVD can offer. A one-sided DVD 5 with 4.7 GB storage
capacity is enough for 4 Minutes. For this reason, the available pictorial
material must be effectively compressed – a function which is achieved with
the MPEG procedure.
This procedure is based on the simple fact that up to 96% of digital video data
consists of repetition and can be compressed without visible degradation of
the pictorial quality.
Each MPEG compression is, however, a data reduction and as such
connected with information loss. If the video consists of very extensive details,
or if the content changes very fast, then the picture may blur (dependent on
the strength of the compression and the quality of the encoder).
Errors can also result from so-called compression artifacts such as small color
defects or images that are too dark.
At average compression rates under 3 megabits per second it is probable that
you will notice reduced quality. At rates around 6 megabit per second the
degradation in quality becomes almost invisible.
Interlace
For historical reasons, pictures in a movie are always recorded and
transmitted in the form of two fields; first the lines with even numbers and then
those with odd numbers. These fields are alternatively displayed with double
the frame rate. The (lazy) eye of the viewer or the processing of the TV tube
puts the two frames together to form one.