The heterogeneity in the current and future multimedia environment requires an elegant adaptation framework for the production and consumption of different kinds of multimedia content. Such an architecture is preferably based on the usage of scalable bitstreams and a format-agnostic content adaptation engine. To obtain fully embedded scalable bitstreams, the joint scalable video model (JSVM) has been used in this paper. Hereby, JSVM defines a scalable extension on top of the H.264/AVC specification. This extension will make it possible to create bitstreams that are scalable along the temporal, spatial, and SNR axis. On the other hand, bitstream structure descriptions can be used to realize an elegant and format-agnostic adaptation engine. Such descriptions can be created by making use of the MPEG-21 bitstream syntax description language (BSDL) standard. The latter allows to describe the high-level structure of scalable bitstreams in XML. This paper explains how fully scalable bitstreams can be customized by transforming BSDL-based bitstream structure descriptions. From our performance analysis, one can conclude that the transformation of the XML description, as well as the generation of the adapted bitstream, can be done several times faster than real time