INTERNATIONAL ORGANISATION FOR STANDARDISATION
ORGANISATION INTERNATIONALE DE NORMALISATION
ISO/IEC JTC1/SC29/WG11
CODING OF MOVING PICTURES AND AUDIO
ISO/IEC JTC 1/SC 29/WG 11 N5187
Shanghai, China October 2002
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Title: |
MPEG-21 MDS – Frequently Asked Questions (FAQ) – Version 5.0 |
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Source: |
MDS |
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Editor: |
Niels Rump (Rightscom Ltd.) |
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Status: |
Approved |
Table of content
This document provides answers to Frequently Asked Questions (FAQs) related to MPEG-21 specifications. It is subject to continuous update and improvements. Any comments or suggestions should be forwarded to the MPEG-21 reflector (mpeg-21-list@imec.be) or directly to the FAQ editor (niels.rump@rightscom.com).
The following questions and answers were revised by the Multimedia Description Scheme (MDS) Group during MPEG’s 63rd meeting in Shanghai in October 2002.
Today, many elements exist to build an infrastructure for the delivery and consumption of multimedia content. Before MPEG-21 there was, however, no ‘big picture’ to describe how these elements, either in existence or under development, relate to each other.
The vision for MPEG-21 is to define a multimedia framework that will enable transparent and augmented use of multimedia resources across a wide range of networks and devices used by different communities. The intent is that the framework will cover the entire multimedia content delivery chain encompassing content creation, production, delivery and trade.
The framework will describe how these existing components can be used together. Where gaps exist new standards will be developed by MPEG to satisfy the requirements.
The basic architectural concept in MPEG-21 is the Digital Item.
Digital Items are structured digital objects, including a standard representation and identification, and metadata. They are the basic unit of transaction in the MPEG-21 framework.
Basically, a Digital Item is a combination of resources (such as videos, audio tracks, images, etc), metadata (such as MPEG-7 descriptors), and structure (describing the relationship between resources).
MPEG has identified key areas to be addressed in order to provide an interoperable multimedia framework. These areas are:
1. Digital Item Declaration (a uniform and flexible abstraction and interoperable schema for declaring Digital Items);
2. Digital Item Identification and Description (the ability to identify and describe any entity regardless of its nature, type or granularity);
3. Content Handling and Usage (provide interfaces and protocols that enable creation, manipulation, search, access, storage, delivery, and (re)use of content across the content distribution and consumption value chain);
4. Intellectual Property Management and Protection (the means to enable intellectual property rights on content to be persistently and reliably managed and protected across a wide range of networks and devices – this also includes a Rights Expression Language and a Rights Data Dictionary);
5. Terminals and Networks (the ability to provide interoperable and transparent access to content across networks and terminals);
6. Content Representation (how the media resources are represented);
7. Event Reporting (the metrics and interfaces that enable Users to understand precisely the performance of all reportable events within the framework);
The seven architectural elements – and their role in facilitating Digital Item-related transactions between Users is depicted in the diagram below:
A User in MPEG-21 is anyone that interacts with Digital Items. Hence, a User can be an individual, an organisation, corporation, any community, consortium or even a government. Moreover, Users act in various roles including creators, consumers, rights holders, content providers, distributors, etc.
The MPEG-21 standard has been designated ISO/IEC 21000 and has been divided into the following sub-parts to address specific areas described in Question 3 above:
Additional parts may be started whenever needed.
MPEG-21 is suitable for many types of applications. Some of the use cases that the standard has been developed to satisfy include:
The MPEG standards cover different areas. Broadly speaking, they can be broken into:
MPEG-1, 2, 4 Coding of audio/visual content
MPEG-7 Providing metadata that describes multimedia content
MPEG-21 Providing a framework for the all-electronic creation, production, delivery and trade of content. Within the framework we can use the other standards (including, but not limited to, MPEG) where appropriate.
MPEG-7 deals mainly with providing descriptions of multimedia content. MPEG-21 is much broader and aims to deals with composite units that consist of multiple resources, how the resources are interrelated as well as the methods by which content can be distributed.
Yes; the DID allows the inclusion of metadata expressed in any format, including MPEG-7.
No; MPEG is liasing and collaborating with other standards bodies to expedite the development of this standard and ensure its interoperability with other technologies.
‘Declaring’ a Digital Item is the process of defining the structure of the Digital Item. It enables creators of Digital Items to declare what their Items comprise of and in what relation these components stand to each other.
One very simple example of a Digital Item would be a ‘digital music release’: It could comprise two sound recordings (e.g. sound files coded in MPEG-2 AAC), the cover photograph (using JPEG), a video clip, and a text file containing the lyrics for the songs. The Digital Item could also contain metadata describing the content of the Item.
The structure of the Digital Item allows the User (or the User’s device) to make choices and selections of components within the Digital Item, for example based on his preferences or capabilities (for example if the User wants to transfer the aforementioned music release to a simple portable music player, the terminal would choose to not transfer the video clip onto the device).
Digital Items are declared using the Digital Item Declaration Language (DIDL). Declaring a Digital Item involves specifying its resources, metadata and their interrelationships.
The DIDL is a language based on an XML schema that has developed to allow the declaration of Digital Items within MPEG-21. It is a flexible and general schema that provides the hooks for higher-level functionality.
Several use cases exist for ways in which this can occur. These include:
No. The Digital Item Declaration may contain references that indicate where the resources are located. This means that it is only necessary to distribute the Digital Item Declaration to a user. The user may then retrieve the resources the Declaration describes as required.
The exact mechanism is currently under development. It is already clear, however, that the mechanisms provided by the Digital Item Declaration provides all that is necessary. The current thinking of MPEG experts is that special descriptors (e.g. an IPMP Descriptor).
Answers to on IPMP/REL/DIA-specific FAQs can be found below.
DII allows the unique identification of Digital Items and parts thereof. Such Identification is crucial for many applications, including determining rights holders of the Digital Item and associating Rights Expressions.
No. MPEG-21 DII allows the inclusion of identifiers from existing (as well as newly developed) identification schemes (e.g. ISRC, ISWC, ISAN, ISBN, …). This enables content industries to continue to utilise their existing schemes in the MPEG-21 context.
Many content industries have developed – and successfully deployed – content identification scheme for their respective market segments. MPEG’s DII specification leverages these existing identifier systems.
But MPEG-21 DII does more: While MPEG-21 allows the compilation of Digital Items comprising resources from several content industries (e.g. a digital Item containing a sound recording and a text document), most of the existing identification schemes only allow the identification of content in one segment. MPEG-21’s DII specification allows using the appropriate identifiers for different elements within Digital Items. For example the Digital Item above, comprising a sound recording and a text document, might contain identifiers for the sound recording (i.e. the ISRC) and the underlying musical work (i.e. the ISWC) and an identifier for the text document (i.e. an ISTC).
The Digital Item Declaration (DID) allows the inclusion of identifiers for the item and its resources.
This is done in the Digital Item Declaration. DID allows the inclusion of any metadata (e.g., MEPG-7 descriptions) into a Digital Declaration (see Question 13). Please also note that the Digital Item Declaration in itself is structural metadata of the Digital Item.
MPEG will ensure that standards exist to facilitate searching, locating, caching, archiving, routing, distributing and using content (which can be any media data and/or descriptive data).
MPEG is currently developing a digital rights management framework that will enable all Users to express their rights to, interests in, and agreements related to Digital Items. It will also enable all Users to derive appropriate levels of assurance that those rights, interests and agreements will be persistently and reliably managed and protected across a wide range of networks and devices. The framework includes components such as a Rights Data Dictionary (RDD), Rights Expression Language (REL) and an IPMP Secure Messaging Architecture.
It is a source of precise semantics which can be used to describe both the types of permissions owners may wish to grant to users and the context within which the permissions apply.
The MPEG-21 Rights Data Dictionary specification does two things. Firstly it describes a methodology for creating a structured dictionary of clear, consistent, integrated and uniquely identified terms for the purposes of rights management. Secondly, it supports the MPEG-21 Rights Expression Language and specifies how further Terms may be defined under the governance of a Registration Authority, requirements for which are described in Annex C of the specification.
The dictionary is based on a logical model, the Context Model, which is the basis of the dictionary ontology. The model is described in detail in the specification. It is based on the use of verbs which are "contextualised" so that a dictionary created with it can be as extensible and granular as required.
Terms can be incorporated into the RDD through the agency of a Registration Authority, for which a set of requirements have been developed as an annex to the specification.
When the Registration Authority has been established it will create procedures for this in accordance with the requirements contained in the specification.
The Rights Expression Language is a machine-readable language that can declare rights and permissions for entities to perform acts on resources under conditions.
The MPEG REL has been specifically developed to be scaleable to both increase and decrease the scope of the language as required by a specific application. This can be accomplished by the use of profiles and extensions.
The MPEG REL is not specific to any market or product type. The language has been developed by a group of experts with experience from many disciplines including content, technology and services.
Although the MPEG REL was development for the multi-media industries, the language allows for any group to develop industry specific solutions that leverage the core of the language, for example the standards bodies Open e-Book Forum and TV-Anytime are developing extensions to the MPEG REL.
The MPEG REL provides interoperability across DRM systems and content management systems and components thereof, by providing an unambiguous method to express the permitted uses of Digital Items.
No – The MPEG REL provide the grammar and syntax to express any business model.
No – The MPEG makes no assumption of polices or predetermined usage of Digital Items, but rather allows Users to express permission, terms and conditions of their choice.
The MPEG-21 Rights Data Dictionary provides definitions and semantics for the Rights Expression Language verbs. It enables the generation of additional terms for the REL as and when required.
Rights declarations can assign permissions to digital items and their aggregations, derivations, and parts by using the same identifiers that can be associated to these by using DII within DID.
MPEG is currently developing a messaging architecture that will allow the protection and enforcement of IPMP rights expressed using the RDD/REL. The architecture provides methods to support secure communications between entities in the content chain.
No; the architecture has specifically been designed to be extensible and allow addition of IPMP technologies as they become available.
MPEG-21 will address the issues associated with the provision of content transparently adapted to meet terminal and network requirements (including quality of service). One topic within ‘terminals and networks’ already addressed by MPEG Digital Item Adaptation (DIA).
The overall goal for Terminals and Networks is to enable interoperable and transparent access to resources across networks and terminals. Digital Item Adaptation has been identified as one essential aspect of Terminals and Networks that will provide tools to support resource adaptation, descriptor (‘metadata’) adaptation, and Quality of Service management.
As part of this work item, a description of usage environments, including terminal and network characteristics, as well as information describing user preferences is required. Such descriptions will support resource adaptation and delivery for a variety of application environments and will enable Quality of Service to be managed by the various Users that exchange and process content in the form of Digital Items.
Additionally, this work targets the description of content representation formats to enable their adaptation.
A DIA engine refers to the processor that is responsible for the actual adaptation of Digital Items, which includes resources and descriptions. This engine may consist of separate resource adaptation engines and description adaptation engines. On the other hand, DIA tools will be used by the DIA engines to assist and guide the adaptation process.
It is important to emphasise that the adaptation engines themselves will not be standardised within MPEG-21. However, tools that provide support for Digital Item Adaptation in terms of resource adaptation, descriptor adaptation, and/or Quality of Service management are within the scope of the requirements.
While content description has been addressed by MPEG-7 (see Question 8), the description of content format and usage environments has not been addressed and it is now the target of MPEG-21 Digital Item Adaptation.
With this goal in mind, it is essential to have available not only the description of the content but also a description of its format and of the usage environment in order that content adaptation may be performed to provide the User the best content experience for the content requested with the conditions available.
So far the usage environment descriptor tools have been grouped as:
A. No. DIA is one part of Terminals and Networks - albeit an important one. Another element are mechanisms for ensuring Quality of Service. It is at this point in time unclear, however, if MPEG will develop specifications for QoS.
Content representation is an important part of any multimedia framework. MPEG will ensure that there are content representations available that are suitable to achieve the objectives of MPEG-21.
Every interaction is an event. Arising from this event, there is the opportunity to describe what occurred. MPEG-21 aims to provide the tools to describe and report events as they occur through the MPEG-21 framework.
|
Acronym |
Definition/Meaning |
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AhG |
Ad Hoc Group |
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AM |
Adaptation Model |
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BoG |
Break-out Group |
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CD |
Committee Draft |
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CE |
Core Experiment |
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DIA |
Digital Item Adaptation |
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DID |
Digital Item Declaration |
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DIDL |
Digital Item Declaration Language |
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DII |
Digital Item Identification |
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DIP |
Digital Item Processing |
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IPMP |
Intellectual Property Management & Protection |
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IPMPX |
IPMP Extensions |
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ISAN |
International Standard Audio-visual Number |
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ISBN |
International Standard Book Number |
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ISRC |
International Standard Recording Code |
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ISTC |
International Standard Text Code |
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ISWC |
International Standard Work Code |
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MDS |
Multimedia Description Schemes subgroup of WG11 |
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MPEG |
Moving Picture Experts Group |
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NB |
National (standards) Body |
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PDTR |
Proposed Draft Technical Report |
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RDD |
Rights Data Dictionary |
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REL |
Rights Expression Language |
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TR |
Technical Report |
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TRACS |
Tool Representation and Communication System (part of IPMP) |
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WD |
Working Draft |
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WD |
Working Draft |
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XM |
eXperimentation Model (from MPEG-7) |
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XML |
Extensible Mark-up Language |
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YM |
sYstems and Software Model |
The following table sets out the current timetable for MPEG-21standardisation:
|
Part |
Title |
CfP |
WD |
CD PDAM PDTR |
FCD FPDAM |
FDIS FDAM DTR DCOR |
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1 |
Vision, Technologies and Strategy |
Published |
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2 |
Digital Item Declaration (DID) |
Finalised and awaiting Publication |
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3 |
Digital Item Identification (DII) |
Finalised and awaiting Publication |
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4 |
Intellectual Property Management & Protection Tool Representation and Communication System (IPMP TRACS) |
Dec 02 |
Jul 03 |
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5 |
Rights Expression Language (REL) |
Jul 02 |
Dec 02 |
Jul 03 |
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6 |
Rights Data Dictionary (RDD) |
Jul 02 |
Dec 02 |
Jul 03 |
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7 |
Digital Item Adaptation (DIA) |
May 02 |
Dec 02 |
Mar 03 |
Jul 03 |
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8 |
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If you are a member of MPEG, you may participate in the meetings on the areas of MPEG-21 which are held at the MPEG meetings. You may also by join one of the Ad Hoc Groups, subscribe to various reflectors, and participate in Core Experiments (CEs) depending on your interest.
If you have any further questions, you may send email to the reflector at mpeg-21-list@imec.be or directly to the FAQ editor (niels.rump@rightscom.com).
There are a number of documents available at the MPEG Home Page at http://mpeg.telecomitalialab.com, including:
If you are not yet a member of MPEG, please find information about joining at http://mpeg.telecomitalialab.com/how_to_join.htm.