A real-time XML-based adaptation system for scalable video formats

Scalable bitstreams are used today to contribute to the Universal Multimedia Access (UMA) philosophy, i.e., accessing multimedia anywhere, at anytime, and on any device. Bitstream structure description languages provide means to adapt scalable bitstreams in order to extract a lower quality version. This paper introduces a real-time XML-based framework for content adaptation by relying on BFlavor, a combination of two existing bitstream structure description languages (i.e., the MPEG-21 Bitstream Syntax Description Language (BSDL) and the Formal Language for Audio-Visual Representation extended with XML features (XFlavor)). In order to use BFlavor with state-of-the-art media formats, we have added support for transparent retrieval of context information and support for emulation prevention bytes. These extensions are validated by building a BFlavor code for bitstreams compliant with the scalable extension of the H.264/AVC specification. Performance measurements show that such a bitstream (containing a bitrate of 17 MBit/s) can be adapted in real-time by a BFlavor-based adaptation framework (with a speed of 27 MBit/s).