Today's Internet is accessible to diverse end devices through a wide variety of network types. To react to this diversity of usage contexts new media codecs include adaptation support in the codec design. Scalable media codecs enable to easily retrieve different qualities of the media content by simply disregarding certain media segments. The MPEG-21 Digital Item Adaptation (DIA) standard enables codec-agnostic adaptation by specifying a set of descriptions in order to describe content, adaptation possibilities and usage context in the XML domain. This book extends the DIA approach towards dynamic and distributed environments. To achieve this, novel mechanisms for fragmentation, storage and transport of XML metadata are introduced. Additionally, a mechanism based on a novel binary header to enable codec-agnostic adaptation is specified. This Generic Scalability Header (GSH) enables codec-agnostic adaptation at a considerably lower performance cost compared to the DIA approach. An adaptation node based on these novel mechanisms is implemented and evaluated for several types of scalable media. A concluding discussion analyzes the results of the evaluation of both mechanisms.
