Abstract
The MPEG-21 standard forms a comprehensive multimedia framework covering the entire multimedia distribution chain. In particular, it provides a flexible approach to represent, process, and transact complex multimedia objects which are referred to as Digital Items (DIs). DIs can be quite generic, independent of the application domain, and can encompass a diversity of media resources and metadata. This flexibility has an impact on the level of interoperability between systems and applications, since not all the functionality needs to be implemented. Furthermore, additional semantic rules may be implemented through the processing of the Digital Item which is possibly driven by proprietary metadata. This jeopardizes interoperability and consequently raises barriers to the successful achievement of augmented and transparent use of multimedia resources. In this context, we have investigated and evaluated the interoperability at the semantic level of Digital Items throughout the automated production, delivery and consumption of complex multimedia resources in heterogeneous environments. This paper describes the studies conducted, the experiments performed, and the conclusions reached towards that goal. © Copyright 2008 ACM.

Abstract
Context-aware applications are fast becoming popular as a means of enriching users' experiences in various multimedia content access and delivery scenarios. Nevertheless, the definition, identification, and representation of contextual information are still open issues that need to be addressed. In this paper, we briefly present our work developed within the VISNET II Network of Excellence (NoE) project on context-based content adaptation in Virtual Collaboration Systems (VCSs). Based on the conducted research, we conclude that MPEG-21 Digital Item Adaptation (DIA) is the most complete standardization initiative to represent context for content adaptation. However, tools defined in MPEG-21 DIA Usage Environment Descriptors (UEDs) are not adequate for Virtual Collaboration application scenarios, and thus, we propose potential extensions to the available UEDs.

Abstract
The use of context is already a reality in different application fields. One such example is the Robotics field, where sensors are used to capture information about the surrounding environment, allowing the system to react to changes. But also in the multimedia cornmunications field, some work has recently emerged to allow combining sensed context and use that combined information to decide how to adapt the content. This paper describes the MULTICAO ontology, which lies at the core of an Adaptation Decision Engine, providing it with a formal description of the surrounding environment in a similar way as humans would describe it. This way the system has higher chances to take adaptation decisions that best meet users' expectations.

Abstract
This paper addresses multimedia end user system design for content distribution over heterogeneous networks and terminals, with particular focus on End-to-End quality of service (QoS) control. A multimedia terminal comprising content-related metadata processor, usage environment characteristics provider, end user QoS monitor and H.264's extension Scalable Video Coding (SVC) audio-visual player in coordination under a terminal middleware, has been conceived and implemented. This end user terminal enables End-to-End QoS control for content adaptation solution both in semantic and physical approaches to maximize end user's perceptual experience and minimize resources. Such design approach illustrates a possible architecture for next generation multimedia end user terminal supporting MPEG-21 and H.264's extension SVC codec standards.

Abstract
With the advent of the World Wide Web (WWW), large volumes of multimedia content are now available on-line in multiple formats. Furthermore, with the proliferation in the mass market of a diversity of multimedia-enabled end-user devices, consumers increasingly expect to be able to access any kind of content anywhere and at any time, regardless of the capabilities of their terminals and the networks to which they are attached. Access to content that meets user expectations and demands, must take into account all the different aspects of this Peterogeneous environment. This paper describes the approach adopted within the European project ENTHRONE-2 to address this challenge. ENTHRONE-2 has conceived, designed and implemented a distributed platform, based on open standards, notably MPEG-21 and Web Services technologies, that supports the kind of network multimedia content access users expect. In particular, it focus on the ENTHRONE Integrated Management Supervisor, the entity that coordinates all the actions required for the provision of quality and context-aware, multimedia services to end-users.

Abstract
This paper addresses the inter-operability problem of multimedia terminal in media content delivery over heterogeneous networks and devices. We design and implement a terminal which includes a content browser providing presentation, navigation and interaction with MPEG-21 Digital Item Declaration (MPEG-21 DID) in order to support universal media access (UMA). We optimized the architecture in a client-server distributed approach with Web Service support. This terminal enables the MPEG-21 standard compliant content accessible on different terminal devices via common Web browsers. Such a design strategy illustrates a next-generation multimedia terminal supporting inter-operability in multimedia content adaptation over a heterogeneous delivery chain.