Chapter 3: MPEG-21: The Multimedia Framework Standard

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Overview

MPEG-21 ^[1], ^[2] is the ISO/IEC 21000 standard from the Moving Picture Experts Group (MPEG) that defines an open multimedia framework. The driving force for MPEG-21 was the current situation: Many elements exist to build an infrastructure for the delivery and consumption of multimedia content, but there exists no "big picture" to describe how these elements relate to each other.

The vision for MPEG-21 is to define an open multimedia framework that will enable transparent and augmented use of multimedia resources ^[3] 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, personalization, consumption, presentation, and trade.

MPEG-21 does not intend to specify the total behavior of a distributed multimedia system, but to define where standards are required in a multimedia framework. The normative methods and descriptions proposed are capable of supporting the delivery of digital content in a more interoperable and fair way than it is practiced today. For this, it is necessary to reach a shared vocabulary among the users of a distributed multimedia system. This presents a difficulty, as there are many examples of different architectures that evolve in response to a variety of models for the use of content. For instance, we have seen in the introduction (Chapter 1) that there are at least three models employed for supporting multimedia resource discovery (Dublin Core, SMPTE [Society of Motion Picture and Television Engineers], and MPEG-7). To avoid giving undue preference to one model above another, MPEG-21 proposes to describe the multimedia framework as a generic architecture. This includes first the introduction of an interoperable unit of exchange, the digital item (DI), which is a hierarchical container of resources, metadata, and other digital items. Further parts of the architecture are the digital item declaration (DID), which serves to declare a DI; the identification of DIs; digital rights management (DRM) and intellectual property management and protection (IPMP) of DIs; personalization of DIs; adaptation of DIs to resource constraints; and further tools for management of DIs.

The next sections detail the different parts of the MPEG-21 standard and relate them to each other to show the "big picture" of the multimedia framework. Section 3.1 gives the essential concepts of MPEG-21, introduces the structure of MPEG-21, and gives the current status of the 12 parts of MPEG-21. Section 3.2 presents the DID specification and shows a practical example. Section 3.3 introduces the IPMP and the rights expression language (REL) and data dictionary. Section 3.4 explains the elements of the digital item adaptation and gives a comprehensive example. Section 3.5 relates the various MPEG standards to each other. Finally, Section 3.6 gives examples of ongoing MPEG-21 research projects.

^[1]Pereira, F., The MPEG-21 standard: why an open multimedia framework?, in Proceedings of the 8th International Workshop on Interactive Distributed Multimedia Systems (IDMS 2001), LNCS 2158, Lancaster, September 2001, Springer-Verlag, Heidelberg, pp. 219–220.

^[2]Hill, K. and Bormans, J., Overview of the MPEG-21 standard. ISO/IECJTC1/SC29/WG11 N4041 (Shanghai Meeting), October 2002, http://www.chiariglione.org/mpeg/.

^[3]Resource in the MPEG-21 jargon corresponds to an identifiable media resource; that is, image, video, audio, or other media asset.

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