The use of Regions Of Interest (ROIs) is a useful concept for many application scenarios, especially for those applications that are deployed in heterogeneous multimedia environments. In this paper, we show how Flexible Macroblock Ordering can be used in the scalable extension of the H.264/AVC specification in order to define the ROIs in the coded bitstream. Furthermore, we introduce an XML-driven adaptation framework based on the MPEG-21 Bitstream Syntax Description Language in order to implement the ROI extraction process. This framework gives us the opportunity to adapt scalable bitstreams by using an engine that has no knowledge of the underlying coding format. From the performance analysis of our adaptation framework, we can conclude that the ROIs can be extracted in the XML domain and that the ROIs in the adapted bitstream are still intact without quality degradation. Furthermore, the traditional drifting problem caused by the ROI extraction can be neglected. Finally, we show that the adaptation process in the XML domain can be executed in real time.
展开▼
