Moving Picture Experts Group - MPEG
Moving picture experts
group (MPEG) standards are digital video encoding processes that
coordinate the transmission of multiple forms of media (multimedia).
MPEG is a working committee that defines and develops industry standards
for digital video systems. These standards specify the data compression
and decompression processes and how they are delivered on digital
broadcast systems. MPEG is part of International Standards Organization
(ISO).
The MPEG system defines
the components (such as a media stream or channel) of a multimedia
signal (such as a digital television channel) and how these channels are
combined, transmitted, received, separated, synchronized and converted
(rendered) back into a multimedia format.
The basic components
of a MPEG system include elementary streams (the raw audio, data or
video media), program streams (a group of elementary streams that
make up a program) and transport streams that carry multiple
programs.
This figure shows
the basic operation of an MPEG system. This diagram shows that the MPEG
system allow multiple media types to be used (voice, audio and data),
codes and compresses each media type, adds timing information and combines
(multiplexes) the media channels into a MPEG program stream. This example
shows that multiple program streams (e.g. television programs) can be
combined into a transport channel. When the MPEG signal is received, the
program channels are separated (demultiplexed), individual media channels
are decoded and decompressed and they are converted back into their
original media form.
MPEG
System Diagram
The MPEG system has
dramatically evolved since 1991 when it was introduced primarily for use
on compact disk (CD) stored media. The first version of MPEG, MPEG-1,
was designed for slow speed stored media with moderate computer
processing capabilities.
The next evolution of
MPEG was MPEG-2, which allowed television broadcasters (such as
television broadcasters, cable television and satellite television
providers) to convert their analog systems into more efficient and
feature rich digital television systems.
Since its introduction,
the MPEG-2 system has evolved through the use of extensions to provide new
capabilities. The term MPEG-2.5 is a term commonly used to describe an
interim generation of MPEG technology that provides more services and
features than MPEG-2 but less than the MPEG-4.
The development of an MPEG-3
specification was skipped. MPEG-3 was supposed to be created to enhance
MPEG-2 to offer high definition television (HDTV). Because HDTV capability
was possible using the MPEG-2 system, MPEG-3 was not released.
The next progression of
MPEG technology was the release of the initial parts of the MPEG-4
specification. The MPEG-4 specification allows for television transmission
over packet data networks such as broadband internet. The initial
release of the MPEG-4 system did not offer much improvement over the
MPEG-2 video compression system.
To develop this more
efficient video compression technology for MPEG-4, a joint video committee
was created. This joint video committee was composed of members from the
IETC and ITU for the purpose of analyzing, recommending, solving technical
issues to create an advanced video compression specification. The result
of this joint effort was the production of the advanced video coder (AVC)
that provides standard definition (SD) quality at approximately
2 Mbps. This new part of MPEG-4 video compression (part 10) technology
is approximately 50% more efficient (higher compression ratio) than MPEG-2
video coders. The version of AVC defined by the ITU is called H.264.
This figure shows
how the video coding developed for MPEG-4 was a joint effort between the
ISO/IEC and United Nations ITU. Both groups worked together to produce the
video coding standard. The ISO/IEC version is called advanced video coding
(AVC) and the ITU version is called H.264.
MPEG
Joint Video Committee
There are other MPEG
industry standards including MPEG-7, which is adds descriptions
to multimedia objects and MPEG-21, which adds rights management
capability to MPEG systems.
This figure shows
how MPEG systems have evolved over time. This diagram shows that the
original MPEG specification (MPEG-1) developed in 1991 offered medium
quality digital video and audio at up to 1.2 Mbps, primarily sent via CD
ROMs. This standard evolved in 1995 to become MPEG-2, which was used for
satellite and cable digital television along with DVD distribution. The
MPEG specification then evolved into MPEG-4 in 1999 to permit multimedia
distribution through the Internet. This example shows that work continues
with MPEG-7 for object based multimedia and MPEG-21 for digital rights
management.
MPEG
Evolution Diagram
Related MPEG Definitions
Intra Frames - I-Frames
Predicted Frames - P-Frames
Bi-Directional Frames - B-Frames
DC Frames - D-Frames
Group
of Pictures - GOP
Musicam
Elementary
Stream - ES
Transport
Stream - TS
MPEG
Transmission
MPEG
Layer 3 - MP3
MPEG Books
more
details
|
Introduction
to MPEG
This
book explains the basics of audio and video digitization and compression and
the standard formats that are used be MPEG. You will learn about the different
MPEG audio coders and video coder options.
|
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