数字媒体适配过程的一般框架、模型及应用研究

General Framework,Mathematical Model,Current Activities and Open Issues for Media Adaptation in MPEG-21 DIA

丰富的媒体内容和格式、异构的网络以及多样的终端设备,成为通用媒体访问的巨大障碍,媒体适配成为必要.文中分析了MPEG-21数字媒体适配DIA各实体之间的抽象关系,讨论了数字媒体适配的一般框架,建立了基于混合变量的约束优化模型.该模型统一了现有的媒体适配应用研究,能够用一致的算法进行求解.同时,文中从图像理解和视频分析角度,建立了媒体适配的层次结构,对媒体适配应用进行分类,并以当前的主要应用研究如图像适配、视频转码、位率适配、视频对象适配等举例说明.文中也探讨了混合媒体的多模态适配,指出了今后的研究热点和难点,如媒体语义抽取和适配、用户主观测度和媒体访问体验最大化等.

A growing variety of terminals and heterogeneous networks with dynamic throughputs make it a challenge in multimedia contents consumption. Media adaptation has been introduced in order to maximize user experiences and ensure quality of service （QoS） in universal media access environment. Based on the relations among entities such as resources, adaptation operators and utility in MPEG-21 digital items adaptation （DIA）, and the general media adaptation framework, a mixed-variable constrained optimization model is proposed in this paper. The model unifies researches in this field, brings together the problem formulation and solution in a consistent way. A hierarchical adaptation structure is also constructed, from the viewpoints of image understanding and video analysis, and applied to classify some representative media adaptation applications. Leading pursuits such as image adaptation, scalable video transcoding, bit rate adaptation, video objects （VOs） adaptation, multi-modality conversion and fusion of mixed medias, etc. , are illustrated by examples. Hotspots such as semantic abstraction of media contents, measurements of subjective quality, and maximizing of user experiences, etc. , are also addressed.