stands for "motion pictures expert group"
(www.mpeg.org). From this group a file format is developed
for the process of compressing and saving Video- or
Multimedia files (Video, Picture and sound) in high
quality. The MPEG-Standard is divided into four parts:
MPEG-1, MPEG-2, MPEG-3 and MPEG-4 whereby MPEG-3 is
integrated implanted in MPEG-2.
For playing the big data size of movies (90 minutes
of Video, 25 frames per second, high resolution, many
colour result in about 120 GByte) with "normal"
Computers the MPEG codec uses besides JPEG a way for
saving only the changes from picture to picture (not
M-MJPEG): The MPEG-Format saves in regular times of
twelve pictures Intra-Frames (I-Frames); I-Frames are
with JPEG compressed pictures. The pictures between
the Intra-Frames are saved, if possible, not in full
pictures. MPEG saves the information what parts of a
picture are changing from the first and next frame.
For this also "Predicated Frames" and "B-Frames"
(Bi-directional frame) are used. Because of the fact
that this almost never works perfectly is in addition
to that per frame the changed part in JPEG-Coded saved.
With this method it is possible to reduce the data size
for about 99%. The maximal possible compression is at
developed for smooth Video-playing and has the biggest
compression rate. The MPEG-1 compressing or decompressing
is originally used as a hardware-based process. Now
it is possible with the faster Computer CPUs to Compress
and decompress with Software's. The specifications:
Frames, no information between interlaced pictures.
A resolution of 352 x 288, 352 x 240 (SIF-Resolution)
to 3 MBit/s (1,2 MBit/s for a VCD)
most difference between MPEG-1 and MPEG-2 is that
MPEG-2 better works with the in the TV used interlaced
picture. The secret of MPEG-2 is in the compression
of highest quality so that the video material can
be almost 1 : 1 in source quality edited. Consequently
MPEG-2 established to the broadcast standard. The
50 Fields, 25 Frames
1920x1152 and up to 80 MBITs/s (High Definition TV
1440x1440 and up to 60 MBITs/s (HDTV)
720x576 and up to 15MBITs/s (digital TV and DVD-Video)
352x288 and up to 4MBITs/s (S-VHS, SIF)
part of the MPEG-3 which should be used for High Definition
TV-Quality (HDTV) is meanwhile in the MPEG-2-Standard
implemented. MPEG-3 is not MP3!.
is the next version of MPEG-2 and is since 1996 in developing.
Although MPEG-4 was originally set as the coding standard
for audiovisual data with a low bit rate, was the using
much further than only Streaming of linear media files
in Internet- und wireless applications. MPEG-4 consists
for example efficient mechanisms for the compressing
and distribution interactive media content. In addition
to that has MPEG-4 3D-potentials which allows to show
"artificial intelligent" for example in videoconferences.
This happened in a VRML-similar script language.
compression rate is in MPEG-4 not higher than MPEG-2
but sprites can be compressed much better because
for the coding mechanism is available more time. Possibly
it is possible to change to Wavelets. The script language
allows in a few bytes operations like "moving"
faster to finish than the digital compressed form
of the same operation would do.
first implantation of MPEG-4 is since Windows 98 on
every Windows-PC installed and has a limitation 256
Kilobit per second. For a lag-free video in acceptable
quality it is not enough). Since the DivX-Hack it
was possible to set the bit rate up to 6000 KBit/sec.