Reconfigurable video coding: a stream programming approach to the specification of new video coding standards

International audienceCurrent video coding standards, and their reference implementations, are architected as large monolithic and sequential algorithms, in spite of the considerable overlap of functionality between standards, and the fact that they are frequently implemented on highly parallel computing platforms. The former leads to unnecessary complexity in the standardization process, while the latter implies that implementations have to be rebuilt from the ground up to reflect the parallel nature of the target. The upcoming Reconfigurable Video Coding (RVC) standard currently developed at MPEG attempts to address these issues by building a framework that supports the construction of video standards as libraries of coding tools. These libraries can be incrementally updated and extended, and the tools in them can be aggregated to form complete codecs using a streaming (or dataflow) programming model, which preserves the inherent parallelism of the coding algorithm. This paper presents the RVC framework and its underlying data flow programming model, along with the tool support and initial results

System level synthesis of dataflow programs: HEVC decoder case study

International audienceWhile dealing with increasing complexity of signal processing algorithms, the primary motivation for the development of High-Level Synthesis (HLS) tools for the automatic generation of Register Transfer Level (RTL) description from high-level description language is the reduction of time-to-market. However, most existing HLS tools operate at the component level, thus the entire system is not taken into consideration. We provide an original technique that raises the level of abstraction to the system level in order to obtain RTL description from a dataflow description. First, we design image processing algorithms using an actor oriented language under the Reconfigurable Video Coding (RVC) standard. Once the design is achieved, we use a dataflow compilation infrastructure called Open RVC-CAL Compiler (Orcc) to generate a C-based code. Afterward, a Xilinx HLS tool called Vivado is used for an automatic generation of synthesizable hardware implementation. In this paper, we show that a simulated hardware code generation of High Efficiency Video Coding (HEVC) under the RVC specifications is rapidly obtained with promising preliminary results

Efficient Software Implementation of Stream Programs

The way we use computers and mobile phones today requires large amounts of processing of data streams. Examples include digital signal processing for wireless transmission, audio and video coding for recording and watching videos, and noise reduction for the phone calls. These tasks can be performed by stream programs—computer programs that process streams of data. Stream programs can be composed of other stream programs. Components of a composition are connected in a network, i.e. the output streams of one component are sent as input streams to other components. The components, that perform the actual computation, are called kernels. They can be described in different styles and programming languages. There are also formal models for describing the kernels and the networks. One such model is the actor machine.This dissertation evaluates the actor machine, how it facilitates creating efficient software implementation of stream programs. The evaluation is divided into four aspects: (1) analyzability of its structure, (2) generality in what languages and styles it can express, (3) efficient implementation of kernels, and (4) efficient implementation of networks. This dissertation demonstrates all four aspects through implementation and evaluation of a stream program compiler based on actor machines

MPEG Reconfigurable Video Coding

WOS - ISBN: 978-1-4419-6344-4The currentmonolithic 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 a scheme and specification formalism do not enable designers to exploit the clear commonalities between the different codecs, neither at the level of the specification nor at the level of the implementation. Such a problem is one of the main reasons for the typical long time 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 ISO/IEC MPEG committee, called 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. The RVC framework is based on the usage of a new actor/dataflow oriented language called CAL for the specification of the standard library and the instantiation of the RVC decoder model. CAL dataflow models expose the intrinsic concurrency of the algorithms by employing the notions of actor programming and dataflow. This chapter gives an overview of the concepts and technologies building the standard RVC framework and the non standard tools supporting the RVC model from the instantiation and simulation of the CAL model to the software and/or hardware code synthesis

Orcc: multimedia development made easy

International audienceIn this paper, we present Orcc, an open-source development environment that aims at enhancing multimedia development by offering all the advantages of dataflow programming: flexibility, portability and scalability. To do so, Orcc embeds two rich eclipse-based editors that provide an easy writing of dataflow applications, a simulator that allows quick validation of the written code, and a multi-target compiler that is able to translate any dataflow program, written in the RVC-CAL language, into an equivalent description in both hardware and software languages. Orcc has already been used to successfully write tens of multimedia applications, such as a video decoder supporting the new High Efficiency Video Coding standard, that clearly demonstrates the ability of the environment to develop complex applications. Moreover, results show scalable performances on multi-core platforms and achieve real-time decoding frame-rate on HD sequences

Fast Hardware implementation of an Hadamard Transform Using RVC-CAL Dataflow Programming

International audienceImplementing an algorithm to hardware platforms is generally not an easy task. The algorithm, typically described in a high-level specification language, must be translated to a low-level HDL language. The difference between models of computation (sequential versus fine-grained parallel) limits the efficiency of automatic translation. On the other hand, manual implementation is time-consuming, because the designer must take care of low level details, and write test benches to test the implementation's behavior. This paper presents a global design method going from high level description to implementation. The first step consists in describing an algorithm as a dataflow program with the RVC-CAL language. Next step is the functional verification of this description using a software framework. The final step consists in an automatic generation of an efficient hardware implementation from the dataflow program. The objective was to spend the most part of the conception time in an open source software platform. We used this method to quickly prototype and generate hardware implementation of the Hadamard transform, an algorithm used in many signal processing algorithms, from an RVC-CAL description

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

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