Abstract
In the area of multimedia computing and communication, one of the major
objectives currently being pursued is Universal Multimedia Access (UMA),
i.e., enabling users to transparently access any kind of content from
anywhere, anytime, with any device. In the course of the MPEG-21
(Multimedia Framework) activities, the ISO/IEC MPEG standardization group
has created essential building blocks toward this goal, mainly metadata
standards. Two of them are worth noting here: (1) the Digital Item
Adaptation (DIA) specification, including normative vocabulary and
formats to describe the multimedia consumption context (device, network,
natural environment characteristics, user preferences) and to steer media
adaptation operations required for UMA; (2) the Rights Expression Language
(REL) and Rights Data Dictionary (RDD) specifications, providing terms
and a language to express permissions on the usage of the media (who,
how, what, under which conditions). In this paper, we describe a recent
MPEG-21 DIA Amendment in this area, specifying description formats for:
(1) multimedia conversion capabilities, which tool or service providers
may use to normatively specify the media adaptation (conversion)
capabilities of their tools or services, respectively; (2) permissions
and conditions for multimedia conversions, which can be utilized by
content providers to determine which adaptations (changes) are permitted
on their contents under what conditions. The latter description format
embeds media adaptation descriptions into rights expressions, filling a
gap between DIA and REL/RDD. In the paper, a use case illustrating a
complex UMA scenario justifies the need for these descriptions. Exemplary
conversions and permissions descriptions that apply to this use case as
well as detailed explanations will be given in the main portion of the
paper.