Software Code Generation for the RVC-CAL Language

International audienceThe MPEG Reconfigurable Video Coding (RVC) framework is a new standard under development by MPEG that aims at providing a unified high-level specification of current and future MPEG video coding technologies using dataflow models. In this framework, a decoder is built as a configuration of video coding modules taken from the standard MPEG toolbox library or proprietary libraries. The elements of the library are specified by a textual description that expresses the I/O behavior of each module and by a reference software written using a subset of the CAL Actor Language named RVC-CAL. A decoder configuration is written in an XML dialect by connecting a set of CAL modules. Code generators are fundamental supports that enable the direct transformation of a high level specification to efficient hardware and software implementations. This paper presents a synthesis tool that from a CAL dataflow program generates C code and an associated SystemC model. The generated code is validated against the original CAL description simulated using the Open Dataflow environment. Experimental results of the translation of two descriptions of an MPEG-4 Simple Profile decoder with different granularities are shown and discussed

Framework For Efficient Cosimulation And Fast Prototyping on Multi-Components With AAA Methodology: LAR Codec Study Case

pp 1667 - 1671Real-time signal and image applications have significant time constraints involving the use of several powerful calculation units. Programmable multi-component architectures have proven to be a suitable solution combining flexibility and computation power. This paper presents a methodology for the fast design of signal and image processing applications. In a unified framework, application modeling, cosimulation and fast implementation onto parallel heterogeneous architectures are enabled and help to reduce time-to-market. Moreover, automatic code generation provides a high abstraction level for users. Finally, the worthwhile nature of Matlab/C language cosimulation is illustrated on a still image codec named LAR

High-level dataflow design of signal processing systems for reconfigurable and multicore heterogeneous platforms

The potential computational power of today multicore processors has drastically improved compared to the single processor architecture. Since the trend of increasing the processor frequency is almost over, the competition for increased performance has moved on the number of cores. Consequently, the fundamental feature of system designs and their associated design flows and tools need to change, so that, to support the scalable parallelism and the design portability. The same feature can be exploited to design reconfigurable hardware, such as FPGAs, which leads to rethink the mapping of sequential algorithms to HDL. The sequential programming paradigm, widely used for programming single processor systems, does not naturally provide explicit or implicit forms of scalable parallelism. Conversely, dataflow programming is an approach that naturally provides parallelism and the potential to unify SW and HDL designs on heterogeneous platforms. This study describes a dataflow-based design methodology aiming at a unified co-design and co-synthesis of heterogeneous systems. Experimental results on the implementation of a JPEG codec and a MPEG 4 SP decoder on heterogeneous platforms demonstrate the flexibility and capabilities of this design approach

Synthesizing Hardware from Dataflow Programs

International audienceThe MPEG Reconfigurable Video Coding working group is developing a new library-based process for building the reference codecs of future MPEG standards, which is based on dataflow and uses an actor language called Cal. The paper presents a code generator producing RTL targeting FPGAs for Cal, outlines its structure, and demonstrates its performance on an MPEG-4 Simple Profile decoder. The resulting implementation is smaller and faster than a comparable RTL reference design, and the second half of the paper discusses some of the reasons for this counter-intuitive result

Synthesizing hardware from dataflow programs: An MPEG-4 simple profile decoder case study

International audienceThe MPEG Reconfigurable Video Coding working group is developing a new library-based process for building the reference codecs of future MPEG standards, which is based on dataflow and uses an actor language called CAL. The paper presents a code generator producing RTL targeting FPGAs for CAL, outlines its structure, and demonstrates its performance on an MPEG-4 Simple Profile decoder. The resulting implementation is smaller and faster than a comparable RTL reference design, and the second half of the paper discusses some of the reasons for this counter-intuitive result

Reconfigurable Video Coding on multicore : an overview of its main objectives

International audienceThe current monolithic and lengthy scheme behind the standardization and the design of new video coding standards is becoming inappropriate to satisfy the dynamism and changing needs of the video coding community. Such scheme and specification formalism does not allow the clear commonalities between the different codecs to be shown, at the level of the specification nor at the level of the implementation. Such a problem is one of the main reasons for the typically long interval elapsing between the time a new idea is validated until it is implemented in consumer products as part of a worldwide standard. The analysis of this problem originated a new standard initiative within the International Organization for Standardization (ISO)/ International Electrotechnical Commission (IEC) Moving Pictures Experts Group (MPEG) committee, namely Reconfigurable Video Coding (RVC). The main idea is to develop a video coding standard that overcomes many shortcomings of the current standardization and specification process by updating and progressively incrementing a modular library of components. As the name implies, flexibility and reconfigurability are new attractive features of the RVC standard. Besides allowing for the definition of new codec algorithms, such features, as well as the dataflow-based specification formalism, open the way to define video coding standards that expressly target implementations on platforms with multiple cores. This article provides an overview of the main objectives of the new RVC standard, with an emphasis on the features that enable efficient implementation on platforms with multiple cores. A brief introduction to the methodologies that efficiently map RVC codec specifications to multicore platforms is accompanied with an example of the possible breakthroughs that are expected to occur in the design and deployment of multimedia services on multicore platforms

Automatic software synthesis of dataflow program: An MPEG-4 simple profile decoder case study

International audienceThe MPEG Reconfigurable Video Coding (RVC) framework is a new standard under development by MPEG that aims at providing a unified high-level specification of current MPEG video coding technologies. In this framework, a decoder is built as a configuration of video coding modules taken from the standard "MPEG toolbox library". The elements of the library are specified by a textual description that expresses the I/O behavior of each module and by a reference software written using the CAL Actor Language. A decoder configuration is written in an XML dialect by connecting a set of CAL modules. Code generators are fundamental supports that enable the direct transformation of a high level specification to efficient hardware and software implementations. This paper presents a synthesis tool that from a CAL dataflow program generates C code and an associated SystemC model. Experimental results of the RVC Expert's MPEG-4 Simple Profile decoder synthesis are reported. The generated code and the associated SystemC model are validated against the original CAL description which is simulated using the Open Dataflow environment

RVC: a Multi-Decoder CAL Composer tool

The Reconfigurable Video Coding (RVC) framework is a recent ISO standard aiming at providing a unified specification of MPEG video technology in the form of a library of components. The word “reconfigurable” evokes run-time instantiation of different decoders starting from an on-the-fly analysis of the input bitstream. In this paper we move a first step towards the definition of systematic procedures that, based on the MPEG RVC specification formalism, are able to produce multi-decoder platforms, capable of fast switching between different configurations. Looking at the similarities between the decoding algorithms to implement, the papers describes an automatic tool for their composition into a single configurable multi-decoder built of all the required modules, and able to reuse the shared components so as to reduce the overall footprint (either from a hardware or software perspective). The proposed approach, implemented in C++ leveraging on Flex and Bison code generation tools, typically exploited in the compilers front-end, demonstrates to be successful in the composition of two different decoders MPEG-4 Part 2 (SP): serial and parallel

Dataflow/Actor-Oriented language for the design of complex signal processing systems

International audienceSignal processing algorithms become more and more complex and the algorithm architecture adaptation and design processes cannot any longer rely only on the intuition of the designers to build efficient systems. Specific tools and methods are needed to cope with the increasing complexity of both algorithms and platforms. This paper presents a new framework which allows the specification, design, simulation and implementation of a system operating at a higher level of abstraction compared to current approaches. The framework is base on the usage of a new actor/dataflow oriented language called CAL. Such language has been specifically designed for modelling complex signal processing systems. CAL data flow models expose the intrinsic concurrency of the algorithms by employing the notions of actor programming and dataflow. Concurrency and parallelism are very important aspects of embedded system design as we enter in the multicore era. The design framework is composed by a simulation platform and by Cal2C and CAL2HDL code generators. This paper described in details the principles on which such code generators are based and shows how efficient software (C) and hardware (VHDL and Verilog) code can be generated by appropriate CAL models. Results on a real design case, a MPEG-4 Simple Profile decoder, show that systems obtained with the hardware code generator outperform the hand written VHDL version both in terms of performance and resource usage. Concerning the C code generator results, the results show that the synthesized C-software mapped on a SystemC scheduler platform, is much faster than the simulated CAL dataflow program and approaches handwritten C versions

An integrated environment for HW/SW co-design based on a CAL specification and HW/SW code generators

The possibility of specifying both SW and HW components using the same language is a very attractive design approach. However, despite the efforts spent for implementing such approach using common programming languages such as C and C++, it has not yet shown to be viable and efficient for complex design. The main reason is the difficulty of expressing architectural properties at the level of a common description, difficulty that finally results into the failure of synthesizing efficient HW and efficient parallel SW. This is not the case for dataflow programming that is well- suited to the description of complex real-world computational systems that may contain appreciable amounts of concurrency. A CAL [1, 2] dataflow program is a collection of actors connected by lossless first-in/first-out (FIFO) communication channels, through which they exchange packets of data called tokens. Each actor executes in a sequence of steps, during which it can (1) consume input tokens, (2) produce output tokens, (3) modify its own local state. Actors strictly encapsulate their state, i.e. they cannot directly use or modify the state of other actors. Consequently, executing actors concurrently does not cause race conditions on any state variables, which makes dataflow an excellent (and scalable) parallel programming model. This in turn is key to the generation of efficient HW and SW implementations. This demonstration presents an integrated environment that embeds the synthesis tool that translates a CAL-based dataflow specification into a heterogeneous implementation, composed by HDL and C codes. The demonstration focuses on the capability of the co-design environment to automatically build an executable heterogeneous system implementation running on a platform composed by a processor and a FPGA platform just by annotating the CAL specification. The possibility of direct synthesis from a high level specification is a crucial issue for enabling efficient re-design cycles that include rapid prototyping and validation of performances of the final implementation. The design approach enabled by such integrated environment is particularly suited for development of complex processing systems such as video codecs. As a case study, the demonstration provides the analysis and validation of different SW and HW partitioning of a MPEG-4 Simple Profile decoder