Dr. Thierry Dumas Profile

Dr. Thierry Dumas

at InterDigital Inc

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Proceedings Article | 3 October 2022 Presentation + Paper

Improving reference picture resampling (RPR) for future video coding

Philippe Bordes, Hassane Guermoud, Franck Galpin, Thierry Dumas, Fabrice Urban

Proceedings Volume 12226, 1222608 (2022) https://doi.org/10.1117/12.2632283

KEYWORDS: Video coding, Video, Image processing, Computer programming, Super resolution, Standards development, Video compression

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Considering industry needs for further coding efficiency improvements, the Joined Exploration Team on Video (JVET) established by ITU-T and MPEG for standardizing VVC, has developed a new Enhanced Compression Model (ECM) based on VVC which is a common area for testing future video coding algorithms. The Versatile Video Coding (VVC) supports Reference Picture Resampling (RPR) to change frame resolution without inserting an Instantaneous Decoder Refresh (IDR) or Intra Random Access Picture (IRAP). This feature is particularly well adapted to video streaming and low delay scenarios since it allows seamless frame-based bit-rate adaptation, whereas traditional techniques based on streams switching between coded video chunks at fixed resolution can generate bitrate leaps. ECM implements several new tools that improve the coding efficiency compared to VVC, but some of them were not designed to support RPR. In this paper, we first discuss some necessary adaptations to implement RPR in ECM for these new coding tools. At low bit rate, RPR may improve the coding performance of ECM for luma component, and the coding complexity is reduced. However, RPR may show PSNR drop for chroma component because it performs an additional down-scaling filtering on samples that were already filtered from the original canonical 4:4:4 content to create the 4:2:0 format. Then, in a second part, some modifications of RPR to re-scale luma and chroma differently are proposed. It is shown that it improves ECM efficiency in the context of both super-resolution and low-delay coding use cases.

Proceedings Article | 21 August 2020 Paper

Multiple constraints rate distortion optimization for a video encoder control

Fabrice Le Léannec, Tangi Poirier, Franck Galpin, Fabrice Urban, Julien Fleureau, Gagan Rath, Thierry Dumas

Proceedings Volume 11510, 115101A (2020) https://doi.org/10.1117/12.2568012

KEYWORDS: Distortion, Computer programming, Video coding, Copper, Video, Visualization, Quantization, Volume rendering

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Current video coding standards like HEVC, VP9, VVC, AV1, etc., involve partitioning a picture into coding tree units (CTU), typically corresponding to 64x64 or 128x128 picture areas. Each CTU is partitioned into coding blocks following a recursive coding tree. In recently published perceptual video encoding methods, the CTU is used as the spatial unit to assign a QP value in a given picture area. Such an approach fits well with the usual rate distortion optimization used to decide the coding tree representation of a CTU since a constant QP is used inside the CTU. Thus Lagrangian rate distortion optimization works in such a situation. However, for some applications, finer spatial granularity may be desired with an adaptive QP. A perceptual video coding scheme may use a codec agnostic QP allocation process that proceeds on a 16x16 block basis. The issue raised in such a case is that the rate distortion trade-off among split modes no more works with the Lagrangian method. This paper proposes several methods to perform the rate distortion optimization of a coding tree in the situation where multiple QPs may be assigned inside the same CTU. First a theoretical method to solve the problem is described. It consists in a coding tree RD optimization using multiple Lagrange parameters. Then some simpler empirical methods which emulate the theoretical approach are proposed. Experimental results show the benefit of the proposed methods on top of VP9 and HEVC video encoders.

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