We present a trajectory from formal specification to component, which can be used to prototype applications which combine off-the-shelf components and custom hardware, provided they meet the constraints of Synchronous Data Flow. The formal specification allows us to prove that custom components will be correctly synchronized in a system context. We first introduce VLSI Synchronous Data Flow, elaborate the constraints it imposes, and define functions relevant to constructing a system. Then we describe the construction of a simulation model. Finally, we develop a component for motion video coding in VHDL, starting from a formal specification.