Multiple Transform Selection concept modeling and implementation using Interface Based SDF graphs

Abstract

Recent studies predict that video data accounts for 82% of Internet traffic by 2022. This fact has motivated MPEG to define a new Video Coding Standard called Versatile Video Coding (VVC), which will be released by the end of 2020. VVC will offer the possibility to handle new video formats and to improve significantly video compression over its predecessor HEVC. Indeed, the objective is to reduce the necessary bit rate by half, at equivalent quality. These advances require the use of more complex algorithms, although the increase in complexity has been limited throughout the standardization process. In order to decrease the complexity of VVC and consequently the coding execution time, several methods have been introduced at different stages of the encoder. The aim of this paper is to explore the available parallelism of VVC to accelerate the coding and the decoding processes. This paper focuses on the transformation block and more specifically the new concept of Multiple Transform Selection (MTS) introduced by VVC. Moreover, a study of several granularity levels of Interface-Based Synchronous Dataflow (IBSDF) models and their impact on the performances obtained on x86 architectures is presented. IBSDF dataflow graph has been developed to reveal the available parallelism of MTS. The PREESM fast prototyping tool is then used for the mapping and the scheduling of MTS on virtual and real parallel architectures and for generating efficient parallel implementations on real architectures. PREESM has been used in this work to explore the potential parallelism offered by MTS and to prove the efficiency of MTS on multicore x86 architectures. Experimental results show a speed-up close to the optimum.