A comparative study of state-of-the-art adaptation techniques for scalable multimedia streams

Stream adaptation is a key technology for enabling communication between heterogeneous multimedia devices and applications, possibly located in heterogeneous wired or wireless networks. Converting already compressed multimedia streams into a format suitable for a certain receiver terminal and network can be achieved by transcoding or by filtering of media streams. Transcoding allows more flexible adaptation operations but is in general a very CPU-intensive process. Therefore, scalable media formats have been developed, which allow more efficient adaptation of media streams through media filtering. Several filter techniques for specific media formats have been proposed and implemented during the last decade. Recently, the MPEG-21 Digital Item Adaptation standard has defined a set of new tools for multimedia adaptation. In this paper, we provide a comparative study of several adaptation techniques for scalable multimedia streams. We compare generic MPEG-21-based adaptation techniques with filter mechanisms for specific media formats with respect to the required processing resources and scalability. We also compare filter techniques with stream adaptation through transcoding. Moreover, we compare how adaptation of multiple media streams performs on systems with single-core and with multi-core processors.