6.3 Mobility

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6.3 Mobility

An important factor for the design of a distributed MMDBMS is today's mobile society, where access to multimedia services "anytime, anywhere" is becoming increasingly important. Relevant for determining service requirements are the environmental aspects, such as the user's contextual situation (user preferences), available bandwidth of wireless networks, battery power, and other characteristics of mobile devices. [6]

Let us consider a typical mobile MMDBMS application. A mobile user is walking in the streets of Munich. She would like to check what movies are playing tonight. Her location information is used to select the closest cinema. She connects to the Munich Cinema Database Server, and her user preferences specify what type of movies interest her. Derived from her user preferences and her location, a database query is formulated. As a result of this query, a selection of movies is returned to her. The result presentation is adapted to the user preferences. Different forms are possible, including having a quick look at 5 or 10 seconds of key actions or seeing a number of key frames. Finally, she selects a film and buys the tickets electronically.

This simple mobile MMDBMS application requires a lot of metadata to be searched and exchanged. The multimedia database must contain semantic information on the movies, such as the name of the actors playing in the movie, the movie genre, and so on. It must provide a video summarization that matches the user preferences in terms of content as well as delivery format. Finally, the MMDBMS must resolve issues related to terminal capabilities in terms of memory, bandwidth, display capabilities, and so on. From this application scenario, we identify three main information processes that are crucial.

First, the user's contextual information is crucial, as the query conditions vary depending on the user's situation (location, time, etc.). This contextual information has to be attached to the query for efficient query processing. MPEG-21 defines context information for mobile databases. For instance, the factors on which the media needs of a consumer depend (location, time, etc.) are defined; that is, mapping from user factors to media factors is proposed. In mobile environments, various kinds of situations affect the Users request and also terminals are expected to adaptively control the way media and communication processing are handled. These conditions, such as place, time, surrounding, desirable cost, influence retrieval performance and the way how to deliver the media.

Second, content adaptation in a mobile multimedia database system is crucial. Content adaptation is becoming the key technique to guarantee that a user receives only the information that he or she needs. Content adaptation also means that the delivered content is dynamically adapted to the resource availability (e.g., through transcoding). This book demonstrated that content adaptation may be effectively supported by MPEG-7, which offers metadata for describing the different variations of the audiovisual material (see Chapter 2), and by MPEG-21, which, proposes a frame-work for distributed adaptation through Digital Item Adaptation (see Chapter 3).

Third, real-time retrieval in mobile environments requires the compact and scalable representation of media and metadata. Thus, new scalable media coding standards are under study within MPEG-21 and shall improve the efficiency of the content delivery and simplify considerably the content adaptation process. Moreover, metadata must be compactly packed. In this context, MPEG-7 proposes the BiM (Binary Format for MPEG-7) for efficiently streaming large Extensible Marketing Language (XML)-based data (see Section 2.7).

Finally, let us remark that true peer-to-peer delivery in mobile environments becomes current practice. Thus, the content delivery chain is no longer one-way, but may change direction in one single database session. To illustrate this, let us return to the first use case example of Chapter 1, which was reconsidered on several occasions further along in the book. A mobile and music-interested user records 10 seconds of a song melody she remembers. To identify the content, she sends the recorded audio piece to an audio recognition service (e.g., the "Music Scout" service from net mobile). If the connection is not lost, she will get a prompt and hopefully positive content identification via SMS (Short Message Service), including the title, the songwriter, and a handle to download the complete version. Let us further assume that the user agrees to download the full version at a low price. Then she will receive an MPEG-1 Audio layer-3 (MP3) file at her mobile phone and is provided with a secure link for downloading the song in a better-quality version later on her desktop at home.

The audio material in this use case is once recorded on the mobile phone and is sent to the recognition database for query and later storage and, once the audio material is downloaded from a music provider server, for local use. Thus, the media delivery in the same session is bidirectional. This example also shows another direction of research that is crucial for future applications. It is the development of persistent storage and management of multimedia resources and metadata in mobile devices; thus, the development of solutions to the question, How can multimedia data be stored persistently, organized and indexed on mobile terminals, and retrieved later?

[6]Perry, M., O'Hara, K., Sellen, A., Brown, B.A.T., and Harper, R., Dealing with mobility: understanding access anytime, anywhere, ACM Trans. Comput. Hum. Interact., 8, 323–347, 2001.



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Distributed Multimedia Database Technologies Supported by MPEG-7 and MPEG-21
Distributed Multimedia Database Technologies Supported by MPEG-7 and MPEG-21
ISBN: 0849318548
EAN: 2147483647
Year: 2003
Pages: 77
Authors: Harald Kosch

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