MPEG-21 digital item adaptation: enabling universal multimedia access
The access devices of today are becoming increasingly sophisticated. Thanks to multimedia, communication is much widespread and therefore more powerful. However, we face a serious problem of heterogeneity in our terminals, in our networks, and in the people who ultimately consume and interact with the information presented to them. In this article, we focus on Part 7 of the MPEG-21 standard (ISO/IEC 21000-7), which we refer to as Digital Item Adaptation (DIA). At the time of this writing, the DIA specification is at the penultimate stage of Final Committee Draft (2003); final approval is scheduled for December 2003. The general DIA concept is that Digital Item is subject to both a resource adaptation and a descriptor adaptation engine, which together produce the adapted Digital Item. Note that the standard specifies only the tools that assist with the adaptation process, not the adaptation engines themselves. Digital Item Adaptation (DIA) specifies the following natural environment description tools: location and time and audiovisual environment. The DIA offers a rich set of tools to assist with the adaptation of Digital Items. It offers standardized tools for the description of usage environments, tools to create high-level descriptions of the bitstream syntax to achieve format-independent adaptation, tools that assist in making tradeoffs between feasible adaptation operations and constraints, tools that enable low-complexity adaptation of metadata, and tools for session mobility. Moving forward, the MPEG-21 committee is considering amendments to the specification-for instance, tools that provide further assistance with modality conversion and tools that relate more specifically to the adaptation of audio and graphics media. Furthermore, also being actively considered is how to express the rights that a User has to perform adaptation and how this expression fits into a system that governs those rights.