MPEG Standardization Development
Digital video and audio coding technology has a long research
history and international standards have also been established. It can
be said that all of the effort involved with this finally culminated
in the MPEG scheme. MPEG (Moving Picture Experts Group) is a byname
of a joint technical committee subsidiary group of the International
Organization for Standardization (ISO) and the International Electrotechnical
Commission (IEC). Since the end of the 1980's, the MPEG-1, MPEG-2, and
MPEG-4 standards were developed through the dozens of meetings and numerous
between meeting discussions accomplished by e-mail throughout most of
the decade. Standardization of the MPEG-7 system will follow the above-mentioned
systems, and it will regulate contents description data formats that
support video and audio content retrieval.
Up to now, our laboratories have contributed to the standardization
activity in MPEG. We will contribute continuously in the future.
(January, 1988-November, 1992)
CD-ROM, Video Karaoke
SIF video (horizontal 352 vertical
Editing/random access feasible
|MPEG-1 standard was designed to store video data on
CD-ROM, and later became a foundation for MPEG-2 and newer standards.
MPEG-1 is the byname of the first video coding standard completed by
MPEG. It is a coding format for storage media such as CD-ROMs, and it
compresses video data with half the resolution of SDTV both vertically
and horizontally (SIF) down to approximately 1.5Mbps.
Using a technique called "motion compensation prediction," MPEG-1 first
extracts frames with different image patterns from consecutive frames.
There are two methods of motion compensation: one estimates from the
previous frame and the other estimates from the previous and preceding
frames (bi-directional prediction). Additionally, it classifies this
selected information utilizing a DCT (Discrete Cosine Transform) technique
based on the relevance to human visual perception. By omitting extraneous
information using human visual peculiarity, drastic data compression
is accomplished by means of MPEG-1.
Although MPEG-1 picture quality is inadequate for regular broadcasting
due to the significant data reduction, and utilization of MPEG-1 is
limited only to broadcasting data retrieval, MPEG-1 is the very foundation
of the MPEG-2 encoding standards and those that followed.
(July, 1990-November, 1994)
Digital broadcasting, DVD
General-purpose coding with varied resolution and functions
Addition of functions for studio production.
Addition of stereo video coding function.
|MPEG-2 is a general-purpose coding standard that absorbed
data hierarchical functions in addition to managing Standard TV
(SDTV) and HDTV video data. Digital broadcasting throughout the
world has adopted the MPEG-2 system.
While MPEG-1 was a coding standard for storage media, MPEG-2 was designed
with the aim of expanding the general-purpose coding scheme, making
it applicable to various other media fields including broadcasting.
Its standardization was advanced in cooperation with other international
standardization organizations such as the ITU-R and the ITU-T. The MPEG-2
system manages a wide range of video input images, from SIF to HDTV.
The data compression technique is based on the MPEG-1 format, and it
also includes a system that efficiently codes interlaced images (which
comprise a normal television signal). Furthermore, it introduced a hierarchical
(scalable) coding function enabling a low quality partial reproduction
of coded information to be completely reproduced as high-quality images.
Since MPEG-2 covers a wide range of applications, some of its functions
are unnecessary depending on how it is used. Therefore, multiple subset
standards are defined within the system and utilized by the application
of two indexes: one is a profile index that indicates the degree of
functionality, and the other is a level index that establishes object
image resolution. For example, the above-mentioned bi-directional prediction
cannot be accomplished in a simple-profile, but only in a main-profile.
A main-level is able to handle video inputs up to the point of SDTV,
and a high-level up to HDTV images. The MPEG-2 standard has been adopted
for use in digital broadcasting worldwide.
|Figure: Object-based coding system
Portable videophone, internet video, studio production
QCIF (horizontal 176vertical 144
pixels) to HDTV video
CG animation coding, coding of individual component elements
Version 1 (fundamental part) standardized.
Version 2 (function addition) to be standardized.
Version 3 (studio production standard) is under examination.
|While MPEG-2 was hardware-oriented, standardization
of MPEG-4 was initiated endeavoring for a general-purpose coding
method for multimedia data software processing.
In the beginning, the application of MPEG-4 was supposed to be limited
to portable videophones or the Internet, applications consisting of
a lower bit rate than that of MPEG-1. However, high-bit-rate applications
are presently being developed including broadcast program production.
New concept functions are involved with this such as coding schemes
that impede transmission errors. CG animation image coding was also
introduced in addition to MPEG-2 technical improvements such as advanced
motion compensation. In addition to taking note of the coding efficiency,
object-based coding also had been adopted. As shown in the figure, this
technique first divides video images into composing objects such as
a person and a background scene. The system then performs an individual
coded transmission of each object, and the receiver synthesizes the
data to reproduce the desired image. This enables more efficient compression
and various video controls utilizing video component information that
is very useful for program production.
In terms of low-bit-rate applications, there are home video cameras,
Internet video distribution, and next-generation portable videophones,
some of which are already in practical use. I inserted a table of product
examples. There is also a vision of using MPEG-4 for mobile media digital
|Table: MPEG-4 product examples
|Company (product name, etc.)
||In-house education/training, Internet
||Non-linear editing for in-house
education, Intranet distribution
||Recording to Smart Media
||Internet video distribution
(Windows Media Player)
||Mobile satellite broadcasting service
- Program archives
- Program material database
- Home server
- Music database
- Electronic catalogue
Standardization of contents description data
Scheduled to be approved as an international ISO standard.
|MPEG-7 is the fourth MPEG standard. The aforementioned
MPEG-1, MPEG-2, and MPEG-4 were compression coding standards for
actual video and audio data. MPEG-7 is a standard that addresses
content description data that is attached to actual video and audio
MPEG-7, its official name being Multimedia Content Description Interface,
is the fourth MPEG standard. MPEG-1, MPEG-2, and MPEG-4 are compression
coding standards for actual video and audio data. To the contrary, the
MPEG-7 standard covers the content description data that is attached
to multimedia data in various other formats including those of MPEG-1,
MPEG-2, and MPEG-4. Content description data, sometimes referred to
as metadata or an index, is a description of what is included within
the data. To illustrate, if we imagine video, audio, or textual data
that consists of multimedia contents as books in a library, then the
content description data would correspond to a library card. In other
words, by referring to this description data (a library card), retrieval
of multi media contents (books) becomes possible. The MPEG-7 standardizes
the format and description of data in the same manner as a library card
One of the standardization items I will explain here is the "descriptor."
The descriptor is a function that defines and forms the contents description
data. In the context of the previously mentioned library card illustration:
this data will indicate properties such as the "name of a book," "subtitle,"
"author," and "abstract." The Descriptor standardizes the meaning of
each item and the data format that it should be described with (i.e.
the "name of a book" is defined as a title that is written on the front
page of the book, expressed in Japanese characters.) Although this library
card illustration highlights the descriptor's "liberal-art" attributes,
the descriptor for video and audio data involves more "technical" functions.
For example, the size and motion of image subjects in a video are expressed
To have the above-mentioned descriptor adopted as a standard, it is
essential to verify its efficient performance using actual video contents.
The MPEG is pursuing the establishment of the standard while simultaneously
conducting verification tests.
of contents distribution promotion
The MPEG-7 standard is scheduled to be approved as an ISO international
standard in September of 2001. Helping to make this standard useful
to broadcasting systems as well, NHK has given necessary suggestions
and proposals based on its research results.
When MPEG-7 is diffused and its use becomes more common, contents with
better description data attached will probably have a larger audience.
This seems to bring about new possibilities for the contents industry.
Beginning with the standardization of MPEG-7, the marketing targets
that will involve MPEG seem to be global, targets such as providing
general technologies for multimedia contents circulation.
The MPEG is about to start working on a new standard, MPEG-21, in expectation
of the formation of a video/audio contents distribution market. Although
the standards parameters are not yet concrete, discussion is underway
regarding copyright protection technology for contents circulation.