The development of MP3 and JPEG sparked an explosion in digital content on the internet. These early encoding formats have since been joined by many others, including Quicktime, Ogg, MPEG-2 and MPEG-4, which poses an escalating challenge to vendors wishing to develop devices that interoperate with as much content as possible. This paper presents aspects of Reconfigurable Media Coding (RMC), a project currently mat. In other words, an RMC bitstream contains metadata to assemble a decoder from a fundamental building-blocks, as well as a schema that describes the syntax of the content data, and how it may be parsed. RMC makes it easy to extend (re-configure) existing codecs, for example adding error resilienceor new chroma-subsampling profiles, or to build entirely new codecs. This paper addresses the bitstream syntax component of RMC, validating the approach by applying it to the recent MPEG-4 Video simple profile coder.