Generic design of Chinese remaindering schemes

We propose a generic design for Chinese remainder algorithms. A Chinese remainder computation consists in reconstructing an integer value from its residues modulo non coprime integers. We also propose an efficient linear data structure, a radix ladder, for the intermediate storage and computations. Our design is structured into three main modules: a black box residue computation in charge of computing each residue; a Chinese remaindering controller in charge of launching the computation and of the termination decision; an integer builder in charge of the reconstruction computation. We then show that this design enables many different forms of Chinese remaindering (e.g. deterministic, early terminated, distributed, etc.), easy comparisons between these forms and e.g. user-transparent parallelism at different parallel grains

Revisiting the Sample Adaptive Offset post-filter of VVC with Neural-Networks

The Sample Adaptive Offset (SAO) filter has been introduced in HEVC to reduce general coding and banding artefacts in the reconstructed pictures, in complement to the De-Blocking Filter (DBF) which reduces artifacts at block boundaries specifically. The new video compression standard Versatile Video Coding (VVC) reduces the BD-rate by about 36% at the same reconstruction quality compared to HEVC. It implements an additional new in-loop Adaptive Loop Filter (ALF) on top of the DBF and the SAO filter, the latter remaining unchanged compared to HEVC. However, the relative performance of SAO in VVC has been lowered significantly. In this paper, it is proposed to revisit the SAO filter using Neural Networks (NN). The general principles of the SAO are kept, but the a-priori classification of SAO is replaced with a set of neural networks that determine which reconstructed samples should be corrected and in which proportion. Similarly to the original SAO, some parameters are determined at the encoder side and encoded per CTU. The average BD-rate gain of the proposed SAO improves VVC by at least 2.3% in Random Access while the overall complexity is kept relatively small compared to other NN-based methods

Simulation of the aeroelastic behavior of a possibly detached flow airfoil by a discrete vortex method

International audienceThe aeroelastic behavior of an airfoil results in a complex coupling between the elastic response of the structure and the dynamics of the flow. It can lead to the failure of a lifting surface which consequences could be catastrophic. Experiments and high-order computations contribute to the understanding of this phenomenon, but fast low-order methods are needed for engineering tasks. In the present work, we implement a loose fluid-structure coupling between a discrete-time vortex method, using a leading edge shedding criterion, and the structure motion equations. For each time step, the aerodynamic coefficients are first calculated before the computation of the motion of the structure. Flutter velocity is obtained with the same precision as unsteady standard method. The advantage of the method proposed is the ability to catch the limit cycle for velocities larger than flutter speed due to dynamic stall of the airfoil