International audienceAlthough multi-core processors are now available everywhere, few applications are able to truly exploit their multiprocessing capabilities. Dataflow programming attempts to solve this problem by expressing explicit parallelism within an application. In this paper, we describe two scheduling strategies for executing a dataflow program on a single-core processor. We also describe an extension of these strategies on multi-core architectures using distributed schedulers and lock-free communications. We show the efficiency of these scheduling strategies on MPEG-4 Simple Profile and MPEG-4 Advanced Video Coding decoders

Multimedia applications and embedded platforms are both becoming very complex in order to improve user experience. Thus, multimedia developers need high-level methods to automate time-consuming and error-prone tasks. Dynamic dataflow modeling is attractive to describe complex applications, such as video codecs, at a high level of abstraction. This paper presents a dataflow-based design approach to implement video codecs on embedded multi-core platforms. First, we introduce a custom architecture model to design lowpower multi-core chips based on distributed memory and Transport-Triggered Architecture processor cores. Then, we describe software synthesis techniques to improve dynamic dataflow implementations. This methodology has been implemented into open-source tools and demonstrated on video decoders based on the MPEG-4 Visual standard and the new High Efficiency Video Coding standard. The simulations achieve real-time decoding (40FPS) of high definition (720P) MPEG-4 Visual video sequences on a custom multi-core platformWe would like to thank the organizations which have partially funded this work such as the Center for International Mobility (CIMO) and the Academy of Finland (funding decision 253087). We would also give special thanks to the Orcc and TCE communities as a whole for actively participating in the development of the tools which offers solid basements to this work. clocked at 1Ghz, which is an improvement of more than 100% over previously proposed implementations.

The emergence of massively parallel architectures, along with the necessity of new parallel programming models, has revived the interest on dataflow programming due to its ability to express concurrency. Although dynamic dataflow programming can be considered as a flexible approach for the development of scalable applications, there are still some open problems in concern of their execution. In this paper, we propose a low-cost mapping methodology to map dynamic dataflow programs over any multi-core platform. Our approach finds interesting mapping solutions in few milliseconds that makes it doable at regular time by translating it in an equivalent graph partitioning problem. Consequently, a good load balancing over the targeted platform can be maintained even with such unpredictable applications. We conduct experiments across three MPEG video decoders, including one based on the new High Efficiency Video Coding standard. Those dataflow-based video decoders are executed on two different platform: A desktop multi-core processor, and an embedded platform composed of interconnected and tiny Very Long Instruction Word -style processors. Our entire design flow is based on open-source tools. We present the influence of the number of processors on the performance and show that our method obtains a maximum decoding rate for 16 processors.