X4

364 Annex: Digital Video and Data Storage
http://pro.magix.com
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.
General notes on AVI videos
The AVI format (Audio Video Interleaved) isn't actually a proper video format!
Rather, it is a so-called "container", where the conventions for transferring
audio and video files to the program are only loosely defined. The codec
(coder/decoder) actually defines what storage format is used. A codec
compresses audio/video data into its own unique format which can only be
read by the codec itself and is decoded when the film is played.
In concrete terms, a computer-generated AVI file can only be loaded by and
played on a different computer if the same codec is installed on it.
Many codecs (e.g. Intel Indeo
®
video) have now become standard components
of the Windows™ installation. Others like the popular DivX codec are not
standard. If you are generating an AVI file for future play on another computer
using one of these codecs, you should first install this codec on the other PC.
The best method available is to copy the codec installer to your export
directory and burn it every time you create a video disc (slideshow disc) for
play on computers.
You may encounter some problems when using older video editing cards with
codecs which only function with the card’s hardware. Such AVIs can only be