In 2004, ISO/IEC SC29 better known as MPEG started a new standard initiative aiming at facilitating the deployment of multi-format video codec design and to enable the possibility of reconfiguring video codecs using a library of standard components. The new standard under development is called MPEG Reconfigurable Video Coding (RVC) framework. Whereas video coding tools are specified in the RVC library, when a new decoder is reconfigured choosing in principle any (sub)-set of tools, the corresponding bitstream syntax, described using MPEG-21 BSDL schema, and the associated parser need to be respectively derived and instantiated reconfiguration by reconfiguration. Therefore, the development of an efficient systematic procedure able to instantiate efficient bitstream parsing and particularly variable length decoding is an important component in RVC. This paper introduces an efficient data flow based implementation of the variable length decoding (VLD) process particularly adapted for the instantiation and synthesis of CAL parsers in the MPEG RVC framework.