MPEG-21
Miranda
Bucy
There
are many different ways some one can transmit and store visual and audio
information in a digital format.At
the moment there is no clear way of describing how these different components
fit together.Currently under development
is MPEG-21, which has as its purpose to define a multimedia framework to
enable transparent and augmented use of multimedia resources across a wide
range of networks and devices. (MPEG-21
Overview) To understand what is trying to be
accomplished by MPEG-21 we must first understand the group that is producing
it as well as their previous standards.
The
group working on the MPEG-21 standard is the Motion Pictures Expert Group
(MPEG).They are a working group
of the International Organization for Standardization (ISO).Their
formal name is ISO/IEC JTC 1/SC 29/WG 11.They
were established in 1988 with the purpose of developing international standards
for compression, decompression, processing, and coded representation of
moving pictures, audio, and there combinations, in order to satisfy a wide
variety of applications. (MPEG: Achievements and Current Work)They
are succeeding at meeting this goal with every new standard they produce.
MPEG-1
was the first standard undertaken by the Motion Pictures Expert Group.This
standard produced a number of firsts in the area of standardization.It
was the first standard to give an integrated audio-visual solution, first
to define the “receiver” instead of the “transmitter”, first for video
coding independent of video format, first to be jointly developed by all
industries concerned, first to be developed entirely in software, first
to include a software implementation. (Chiariglione, Leonardo) These firsts
make MPEG-1 an important standard for the industry.
This
standard was developed in five parts.Part
one addresses the problem of combining data streams from the video and
audio parts of the standard with the timing information to form a single
stream.After this is accomplished
the data is in a form well suited to digital storage and/or transmission.The
next section specifies a coded representation that can be used for compressing
video sequences.It was designed
to operate principally from storage media offering a continuous transfer
rate of about 1.5 Mbit/s, but can be used more widely because the approach
taken is generic. (Short MPEG-1 description)Part
three specifies the coded representations that can be used for compressing
audio.“Input audio samples are
fed into the encoder. The mapping creates a filtered and sub sampled representation
of the input audio stream. A psycho acoustic model creates a set of data
to control the quantiser and coding. The quantiser and coding block creates
a set of coding symbols from the mapped input samples. The block 'frame
packing' assembles the actual bitstream from the output data of the other
blocks, and adds other information if necessary.”(Short MPEG-1 description)
Part four specifies the tests that can be designed to verify whether bitstreams
and decoders meet the requirements set out in parts one, two, and three.The
last part technically is not a standard, but more like a technical report.It
gives a full software implementation of the first three parts of MPEG-1
standard. (Short MPEG-1 description)
MPEG-1
also shows its importance in the impact it had on the audio-visual industry.Microsoft
has included an MPEG-1 decoder in there Windows 95/98/NT/2000 operating
systems.MPEG-1 Audio, better known
as MP3, is widely used for transmitting music over the Internet.MPEG-1
is also utilized in many video cameras from several different manufacturers.
(Chiariglione, Leonardo)These factors
show MPEG-1’s importance to the industry and helped establish the Motion
Pictures Expert Group as a standardization group.
MPEG-2
was developed to define a coding system for digital transmission of television
resolution pictures.It was developed
in ten parts.The first section is
for combining one or more elementary streams of video and audio along with
other data into single or multiple streams, which are suitable for storage
and/or transmission.This is divided
into two sections:the Program Stream
and the Transport Stream.The program
stream works like the first section of the MPEG-1 standard.It
combines one or more streams with a common time base into a single stream.It
is designed for use in a relatively error-free environment and is suitable
for applications that involve software processing.The
transport stream combines one or more streams with one or more independent
time bases into a single stream.Streams
sharing a common time base form a program.These
streams or designed for use in environments where errors are more likely
to occur, such as storage or transmission in lossy or noisy media.The
second section builds on the powerful video compression capabilities of
MPEG-1, offering a wide range of coding tools.These
tools have been grouped in profiles to offer different functionalities.
Tab.
1 - MPEG-2 Video profiles
|
|
Simple
|
Main
|
SNR
scalable
|
Spatial
scalable
|
High
|
Multiview
|
4:2:2
|
|
High
level
|
|
X
|
|
|
X
|
=====
|
|
|
High-1440
level
|
|
X
|
|
X
|
X
|
|
|
|
Main
level
|
X
|
X
|
X
|
|
X
|
X
|
X
|
|
Low
level
|
|
X
|
X
|
|
|
|
|
Sources: Short
MPEG-2 description.(October 2000).Leonardo
Chiariglione-Convenor.[Online] Available:http://mpeg.telecomitalialab.com/standards/mpeg-2/mpeg-2.htm
The
table above shows the different combinations recognized by the standard.One
additional profile has been added to this standard since its original approval
in 1994.It uses the existing coding
tools but is capable of dealing with pictures having a color resolution
of 4:2:2 and a higher bitrate.MPEG-2
Video was not developed having studio applications in mind, but a set of
comparison tests carried out by the Motion Pictures Expert Group confirmed
that MPEG-2 Video was at least good or better than standards developed
for high bitrate or studio applications.(Short
MPEG-2 description)
The
next part of the MPEG-2 standard is a backwards-compatible multichannel
extension of the MPEG-1 Audio standard.The
following image shows the structure of an MPEG-2 audio black of data demonstrating
this property.
Source:Short
MPEG-2 description.(October 2000).Leonardo
Chiariglione-Convenor.[Online] Available:http://mpeg.telecomitalialab.com/standards/mpeg-2/mpeg-2.htm
Parts
four and five correspond with parts four and five of the MPEG-1 standard.Part
six is the Digital Storage Media Command and Control (DSM-CC).This
is the specification of a set of protocols, which give the control functions
and operations specific to managing MPEG-1 and MPEG-2 bitstreams.Part
seven holds the specifications of a multichannel audio coding algorithm.Part
eight originally planned to be coding of video but was abandoned because
there was insufficient interest from industries.Part
nine is the specification of Real-time Interface (RTI) to Transport Stream
decoder.The final part of the MPEG-2
standard holds the conformance testing for DSM-CC. This last section is
still currently under development. (Short MPEG-2 description)
Like
the MPEG-1 standard, the MPEG-2 standard is widely utilized.It
is the standard used to create Digital Versatile Discs (DVDs) as well as
digital Television.It is also the
standard used in the encoding of standard definition television (SDTV)
along with high definition television (HDTV.The
4:2:2 component set out in part set out in the second section of the MPEG-2
standard is also used in video production.
MPEG-4,
like the standards before it, is widely utilized with in the industry.It
is also the choice of various bodies working on the next generation of
mobile communication devices, as well as, being used in the development
of Microsoft’s Media Player. (Chiariglione, Leonardo) MPEG-4 is also helping
to develop solutions to problems created by video on demand and other related
applications (MPEG: achievements and current work)
The
six parts of the MPEG-4 standard correspond with the first six parts of
the MPEG-2 standard.However, there
are significant differences in content of these sections.MPEG-4
enables the coding of individual objects allowing the coding of visual
information not in the rectangular shape needed for the MPEG-1 and MPEG-2
standards.The same is true for the
audio information.This gives MPEG-4
the tools to encode speech and audio at different rates with different
functionalities.This required the
system part of the standard to add a composition function to the system
part of the MPEG-2 standard.Part
five, on the other hand, contains complete software implementation information
of both encoders and decoders over just the reference software of the previous
two standards.(MPEG: achievements
and current work)
The
unique thing about MPEG-4 is its structured audio.Structured
audio works by describing the calculations that will make a sound, and
then, provides a means to re-create the sound.It
utilizes the programming language SOAL to describe an algorithm that produces
the sound.This approach is a normative
one, which means the sound will be the same, when decoded, whenever and
however it is reproduced. This
method is also resolution-independent because in essence it is a description
of the sound rather than a physical representation of it.This
allows MPEG-4 to be decoded to any sample rate and any bit depth. (Shapton,
Dave)
The
Motion Pictures Experts Group recently completed work on the first six
sections of their newest standard MPEG-7 in July of this year.It
is an audio-visual information representation that differs form previous
standards because it represents not the information itself, but rather
information about the information.Its
complete design has seven parts.The
first part describes the system.Part
two is a description of the definition language.Part
three handles the video and part four handles audio.Five
is the multimedia description schemes.Six
references SW and seven deals with conformance.The
seventh section is scheduled for approval in early 2002. (MPEG: achievements
and current work)Because of the
newness of the standard there are no technologies are currently out there
that are using this standard.I am
sure that it will take off like its predecessors in the industry and be
widely utilized after full acceptance of the standard.
“The
digital market place rewrites existing business models for trading physical
goods with new models for distributing and trading digital content electronically.In
this new market place, it is becoming increasingly difficult to separate
the different intellectual property rights, which are associated with multimedia
content.The quest to bring the consumer
the ultimate experience in multimedia entertainment means that the boundaries
between the delivery of audio sound (music and spoken word), accompanying
artwork (graphics), text (lyrics), Video (visual), and synthetic spaces
will become increasing blurred.New,
complex solutions are required to manage the delivery process of these
different content types in an integrated and harmonized way, entirely transparent
to the consumer of multimedia services.And
this is the only one of the issues that needs to be addressed; there are
others, like finding content and ensuring quality of service.” (Introduction
to MPEG-21)These are the situations
the Motion Pictures Expert Group hopes that MPEG-21 will address.
There
are many elements in existence to build an infrastructure for the delivery
and consumption of multimedia content. There is, however, no “big picture”
to describe how these components, either in existence or under development,
fit together. The aim for MPEG-21 is to describe how these various elements
fit. Where gaps exist, it will recommend which new standards are required.
Then the Motion Pictures Expert Group will develop new standards as appropriate
while other relevant standards may be developed by other bodies. These
specifications will be integrated into the multimedia framework through
collaboration between MPEG and these entities.The
result is an open framework for multimedia delivery and consumption, with
both the content creator and content user as focal points. This open framework
provides creators and service providers with equal opportunities in the
MPEG-21 environment. This will also be to the benefit of the user by providing
them access to a large variety of content in an interoperable manner. (MPEG-21
Digital Item Declaration)Purpose
of MPEG-21 could be described as the integration of the critical technologies
to enable a more transparent and augmented view of multimedia resources
across a variety of networks and devices.This
would support functions such as:content
creation, content production, content distribution, content consumption
and usage, content packaging, intellectual property management and protection,
content identification and description, financial management, user privacy,
terminals and network resource abstraction, content representation and
event reporting.(MPEG-21
Overview)
The
Motion Pictures Exert Group has lain MPEG-21 out in seven parts.The
following picture shows how these seven parts fit together to create a
multimedia framework.
Source:MPEG-21
Overview.(July 2001).Jan
Bormans, Keith Hill.[Online] Available:http://www.cselt.it/mpeg/standards/mpeg-21/mpeg-21.htm
The
first part of MPEG-21 describes the digital item declaration.This
section will sever many purposes.Some
of which are to establish a uniform and flexible abstraction and interoperable
schema for declaring digital items and to ensure that media resources and
descriptive data are full separable.As
well as, to ensure the digital items are open and extensible to any and
all media resources types and description schemas and to ensure that composite
items can be constructed from other items, without losing the structure
and properties of the sub-item.The
second part handles digital item identification and description.This
provides the ability to include data from various sources and in a variety
of formats allowing the binding of existing description schemas to allow
the correct processing of this data.To
operate, agents need a representation of user’s self.This
is knowledge about the specific domain and a standard language that allows
the non-human entities to entertain a dialogue with other non-human entities.This
is the goal of part three.The third
part covers content handling and usage.This
part defies the different interfaces and protocols for searches, storage,
and the management of digital items.These
descriptions will enable users to express their preferences and to locate
relevant content in the network, and enable the integration and interoperability
of different asset management systems as well as many other features.The
fourth part covers intellectual property management and protection.This
section will define the attributes of a trusted environment for persistent
management and protection of digital items, as well as, the attributes
of the different interfaces between the users and the agents.It
will also encompass work for the management and protection of the MPEG-4
standards audio-visual object component and the MPEG-7 standard descriptors,
description schemes, and descriptions component and then adapt this to
MPEG-21.This section will also include
the management and protection of other items such as personal data and
rights to its use.Part four will
specify a framework for the enforcement of the management and protection
of digital items and the interfaces between transaction systems for the
right management and the system that mange and protect digital data.The
next section covers terminals and networks.In
order to achieve the goal of MPEG-21 the Motion Pictures Expert Group must
standardize five items.Section
five outlines these areas.First
they need to standardize the APIs and associated protocols for terminal
Quality of Service (QoS) management.They
must also look at NPIs and associated protocols for the network QoS management
and the APIs and associated protocols for joint terminal and network QoS
management.The forth item that they
need to standardize is the rules for QoS contract negotiation and implementation.Finally
they need to standardize the APIs enabling QoS agent technologies.Part
six of the MPEG-21 standard deals with content representation.The
goal of this section is to provide, adopt, or integrate content representation
technologies able to efficiently represent MPEG-21 content, in a scalable
and error free way.The content representation
of the media resources will be synchronisable and multiplexed to allow
interaction.The last section covers
event reporting.This section should
standardize metrics and interfaces for performance of all reportable events
in the MPEG-21 environment and provide a means of capturing and containing
these metrics and interfaces that refers to the identification of digital
items, environments, processes, transactions, and users.These
metrics and interfaces would enable users to understand the precise performance
of all reportable events within the framework.These
seven areas are laid out in order to reach the goal of MPEG-21, to provide
seamless interaction between many different entities with in the digital
world. (MPEG-21 Overview)
There
will soon be technologies to go along with this standard as it nears its
completion.No one wants to design
a technology that will utilize a standard in its formative stages.The
possibilities of changes or complete abandonment of the standard by the
Motion Pictures Expert Group would make it to costly of a venture for most
business.I am sure that businesses
are keeping a close eye on this standard as it develops and nears completion.They
are probably laying the groundwork for implementation into to technologies
once the standard is complete.I
believe this standard has a lot to offer the industry and will, like the
standards produced before it, be widely used in a Varity of formats.
I
don’t believe this is the last standard we will see from the Motion Picture
Experts Group.People, as a whole,
are never happy with what they have, they always want something better,
faster, cheaper, more efficient, and as long as this is true the Motion
Pictures Expert Group will be developing new standards for our ever changing
wants, needs, and demands.
Bibliography
Chiariglione,
Leonardo.The MPEG (Motion Pictures
Expert
Group)
generation:New information-age elements.[Online]
Available:http://www.iso.ch/iso/en/commcentre/pdf/MPEG0009.pdf
Introduction
to MPEG-21. (January 2000).Leonardo
Chiariglione,
Keith Hill, Rob Koenen.[Online}
Available:http://mpeg.telecomitalialab.com/events/mpeg-21/worksop_anoucment.htm.
MPEG: Achievements
and Current Work.(April 200).
Leonardo
Chiariglione-Convenor. [Online] Available:http://mpeg.telecomitalialab.com/mpeg_general.htm
MPEG-21
Digital Item Declaration CD. (July
2001).Vaughn
Iverson,
Young-Won Song, Rik Van de Walle, Mark Rowe, Doim Chang, Ernesto Santos,
Todd Schwartz.[Online]Available:
http://www.darmstadt.gmd.de/mobile/MPEG7/Documents/n4248.html
MPEG-21 Overview.(July
2001).Jan Bormans, Keith Hill.
[Online]
Available:http://www.cselt.it/mpeg/standards/mpeg-21/mpeg-21.htm
Shapton, Dave.(January
2001).NetNotes. [Online]
Available:http://www.sospubs.co.uk/sos/jan01/articles/netnotes.htm
Short MPEG-1
description.(June 1996).Leonardo
Chiariglione-Convenor.
[Online] Available:http://mpeg.telecomitalialab.com/standards/mpeg-1/mpeg-1.htm
Short MPEG-2
description.(October 2000).Leonardo
Chiariglione-Convenor.[Online]
Available:http://mpeg.telecomitalialab.com/standards/mpeg-2/mpeg-2.htm