Media Adaptation in MPEG-21 DIA, Framework, Activities and Open Issues

In this paper, based on the media adaptation framework and relations among entities in MPEG-21 DIA, two mixed-variable constrained optimization models are proposed, which unify current researches in media adaptation and can be solved by the direct searches. An overview on our work in media adaptation such as rate adaptation of MPEG-4 FGS video, video objects adaptation, etc., are given. Open issues such as the semantic extraction of media contents, measurements on user subjective quality, etc., are also given with thoughtful discussions.