We present a tool-assisted platform-based design flow for embedded multiprocessor applications. The methodology relies on (1) a formal language which provides constructs to specify the platformindependent behavior of an application using an abstract execution model, and to describe the micro-architecture components of the hardware architecture, together with its compilation chain JAHUEL [1], and (2) a component-based meta-model for joint software and hardware performance modelling and analysis, together with its simulation tool P-WARE [2], which provides fast, precise and scalable platform-level simulations. JAHUEL and P-WARE have been successfully used for the design of industrial multimedia and packet-forwarding embedded software on application-specific multiprocessor architectures.