Hardware/software codesign involves various design problems including system specification, design space exploration, hardware/software co-verification, and system synthesis. A codesign environment is a software tool that facilitates capabilities to solve these design problems. This paper presents the PeaCE codesign environment mainly targeting for multimedia applications with real-time constraints. PeaCE specifies the system behavior with a heterogeneous composition of three models of computation. The PeaCE environment provides seamless co-design flow from functional simulation to system synthesis, utilizing the features of the formal models maximally during the whole design process. Preliminary experiments with real examples prove the viability of the proposed technique.