Special issue on context-aware and mobile multimedia databases and services

It is expected in the near future that the number of created digital multimedia content will rise dramatically. Multimedia metadata is currently the only way to cope with problems like semantic-based information retrieval or organization of content, and provides means to specify adaptation and delivery constraints and rules. In parallel, the integration of accurate hand-held positioning within mobile phones, PDAs, portable computer and the like has brought location-based services directly to individuals, transforming the way we work, travel or play. Therefore, the context has become an important element to be considered in mobile applications and scenarios. Its usage provides new hints for search, delivery and consumption to individual user's situations. The papers in this special issue present new and innovative ideas on analysis, indexing and retrieval, and multimedia semantics when considering context and location-based information mobile environments. The paper by Timo Ojala entitled " Case studies on context-aware mobile multimedia services " explores the design, implementation and evaluation of context-aware mobile multimedia services by presenting six actual and challenging case studies on different application domains. The case studies highlight the opportunities that mobile devices equipped with wireless data transmission provide for context-aware and ubiquitous computing. The paper by Christian Timmerer et al. entitled " A Survey on Delivery Context Description Formats – A Comparison and Mapping Model " describe a mapping model among content descriptions formats. In particular, the paper focuses on the whole delivery context (i.e., terminal capabilities, network characteristics, user preferences, etc.) and investigated the two most prominent state-of-the-art description schemes, namely User Agent Profile (UAProf) and Usage Environment Description (UED). The paper by Omar Choudary et al. entitled " Evaluation of Multimedia Features in Mobile Guide Applications " presents an interesting and complete user study for mobile guide applications by comparing the commercial Google Maps and Nokia Maps. In particular the authors identify missing multimedia features in the utilized commercial applications. The paper by Anna Carreras et al. entitled " A MPEG-Based Architecture for Generic Distributed Multimedia Scenarios " presents a new standards-based architecture for a complex and generic distributed multimedia scenario, which combines content search and retrieval, DRM, and context-based content adaptation together. The paper by Albert Hofmann et al. entitled " MPEG-7 and MPEG-4 LASeR for Authoring Interactive Mobile TV Services " presents the porTiVity system which provides strong authoring tools for mobile interactive content allowing attaching interactivity to moving objects in a TV program. …