Towards a Fully MPEG-21 Compliant Adaptation Engine: Complementary Description Tools and Architectural Models

Abstract

Abstract. This paper develops a number of aspects of metadata-driven adaptation within the MPEG-21 framework that we consider are not clearly covered in the standard. Specifically, we introduce three complementary description tools that we have made use of and that we consider would fill certain gaps that we have identified in the standard. Besides, we offer a group of architectural design patterns along with a pragmatic group of considerations that we have gathered during the development of our MPEG-21 compliant adaptation engine.

CAIN-21: An Extensible and Metadata-Driven Multimedia Adaptation Engine in the MPEG-21 Framework

“…In this way, the Content DI will not be modified when the target usage environment (located in a Context DI) changes. Usage examples and further explanations of this mechanism can be found in [24].…”

“…CAIN-21 has introduced an addressing mechanism [24] in which changes in the underlying metadata descriptors will not imply changes in its source code. With this mechanism, metadata is dealt by means of properties.…”

“…Secondly, and more important, the PM implemented in CAIN required changes in the source code of CAIN whenever a new description was added or changed. CAIN-21 has introduced a mechanism [24] in which metadata is dealt through properties stored in the Properties DI (see section 0). In this way, changes in the set of properties managed by the adaptation engine imply only changes in the Properties DI.…”

“…the adaptation capabilities and the properties to be taken into account); (3) the Configuration DI states which terminal, network and user − from the ones available in Context DI − must be used to serve the adaptation. The purpose of the Configuration DI [24] is to decouple the Content DI and the Context DIs. Instead of storing information of the adaptation state in the Content DI (as the MPEG-21 Part-2 Choice mechanism or MPEG-21 Part-7 DIA Configuration do), the Configuration DI stores all the information related to the adaptation that is to be carried out.…”

“…With CAIN-21 more than one Terminal, Network and User elements can be stored in the Usage Environment DI. Once CAIN-21 is deployed in a multimedia system, the target Terminal, Network and User elements can be addressed by means of the Adaptation Request Configuration Tool (ARC Tool) [24].…”