5.6 Summary

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Distributed multimedia database technologies involve network technology, distributed control, multimedia security, multimedia computing, and multimedia content adaptation. This chapter discussed fundamental concepts and introduced VoD systems including video streaming server technology (Section 5.1), multimedia communication and synchronization (Section 5.2), client-design issues—mainly hardware and software requirements and implementations (Section 5.3), and finally, multimedia content adaptation in Section 5.4. With the maturity of these technologies, we are today experiencing multimedia communication such as video conferencing, digital television, distance education, online games, and so forth. Because of the original focus and design of network communication protocol (i.e., TCP/IP), real-time broadband communication is not yet feasible on the current Internet; however we also experience good quality videos on the Internet. This is because of encoding efficiency that has been considerably improved (e.g., with the new MPEG-4 codec available). In addition, scalable coding techniques will provide us in the near future with richer multimedia access than today, access that will be adapted to resource constraints and usage profiles. Moreover, advanced communication protocols, mainly IPv6, are under investigation, which will enable sufficient QoS for multimedia applications, including mobile applications. Finally, in a more general context, content adaptation tools will supply us with universal multimedia access from anywhere at anytime. A major player in the domain of multimedia communication is surely MPEG-21, which proposes an open multimedia framework for interoperable usage of multimedia data, including scalable coding as well as content adaptation.

Universal Multimedia Access (UMA) implies an improved availability of media, often realized through distributed Web spaces. In this context, intellectual properties have to be managed. That means that a distributed multimedia database system has to provide the means to enable content to be persistently and reliably managed and protected across networks and devices. In particular, protection of copyright has to be guaranteed. A promising technology under investigation is the watermark technology. The purpose of such a technology is to embed copyright information into multimedia clips. MPEG-21 integrates intellectual property management and protection, as well as persistence management (watermarking and related technologies to protect the copyright) in one framework. The combination of multimedia communication management together with intellectual property management is one of the main topics of MPEG-21 standardization activities in 2003, and International Standards will be delivered in spring 2004. Such an integrated framework is crucial to multimedia applications. Communication management can no longer be separated from intellectual property and session mobility management for an effective use of multimedia data in today's applications. For instance, consider a person sitting in an international train and downloading the newest Madonna AV clip from a server in the U.S. to her mobile handheld computer. During the download, the train crosses the boarder from Germany to France. Obviously, it is undesirable to have to restart the download in the new network (the France mobile network) and to reauthenticate and renegotiate the rights for download again. The solution to this problem is the employment of session mobility management tools that allow transferring a session to a new network and resolving rights and authentication such that in our case, the download can smoothly continue.

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