This paper presents experimental results related to adaptive video content mapping used as a compression tool for HDR-PQ content. The purpose of adaptive video content mapping is to adapt the video signal dynamically depending on its statistical properties in order to better exploit the signal codewords range. Adaptive video content mapping has been investigated during the Versatile Video Coding (VVC) standard development with two main implementation designs: in-loop mapping, and out-of-loop mapping. In VVC, the in-loop implementation was finally adopted with a tool named “Luma Mapping with Chroma Scaling” (LMCS). Thanks to its in-loop implementation, LMCS offers high flexibility (high temporal adaptivity, content type adaptivity) and implementation benefits (no need to manage multiple conformance points, one after the decoder, and one after a post-decoder inverse mapping). Nevertheless, it was also observed that for HDR-PQ content, out-of-loop mapping can bring additional coding gains. The paper investigates potential synergies between the in-loop LMCS and out-of-loop mapping. Out-of-loop mapping is implemented as a pre-encoding process, with inverse mapping applied as post-decoding inverse process. A Supplemental Enhancement Information (SEI) message is used to convey the out-of-loop mapping data aside from the video bitstream. Performance results are reported for HDR-PQ content, with out-of-loop mapping only, and with out-of-loop mapping combined with LMCS.

This paper describes a new video coding tool in the Versatile Video Coding standard (VVC) named as luma mapping with chroma scaling (LMCS). Experimental compression performance results for LMCS and non-normative examples for deriving LMCS parameter values are also provided. LMCS has two main components: 1) a process for mapping input luma code values to a new set of code values for use inside the coding loop; and 2) a luma-dependent process for scaling chroma residue values. The first process, luma mapping, aims at improving the coding efficiency for standard and high dynamic range video signals by making better use of the range of luma code values allowed at a specified bit depth. The second process, chroma scaling, manages relative compression efficiency for the luma and chroma components of the video signal. The luma mapping process of LMCS is applied at the pixel sample level, and is implemented using a piecewise linear model. The chroma scaling process is applied at the chroma block level, and is implemented using a scaling factor derived from reconstructed neighboring luma samples of the chroma block.

This paper provides a technical overview of a deep-learning-based encoder method aiming at optimizing next generation hybrid video encoders for driving the block partitioning in intra slices. An encoding approach based on Convolutional Neural Networks is explored to partly substitute classical heuristics-based encoder speed-ups by a systematic and automatic process. The solution allows controlling the trade-off between complexity and coding gains, in intra slices, with one single parameter. This algorithm was proposed at the Call for Proposals of the Joint Video Exploration Team (JVET) on video compression with capability beyond HEVC. In All Intra configuration, for a given allowed topology of splits, a speed-up of ×2 is obtained without BD-rate loss, or a speed-up above ×4 with a loss below 1% in BD-rate.

This paper describes the coding block structure used in the joint Qualcomm/Technicolor responses to the JVET call for proposal on video compression with capability beyond HEVC. The proposed block structure relies on the known quadtree plus binary tree (QTBT) block structure and brings some higher degree of flexibility in it. Two sets of partitioning modes extend QTBT: the ternary tree (TT) and the asymmetric binary tree (ABT). The added split modes are used with a normative non-redundancy policy, which ensures any block topology can be reached through a unique series of split modes. Finally, some flexible binary and ternary partitioning is allowed near the bottom and right picture borders. Overall, the proposed split modes, non-redundancy and picture border strategies lead to 19.6% bitrate reduction over HEVC.

A new inter-channel coding mode named LM mode has been intensively explored in the HEVC standardization project. This mode predicts the chroma signal from the luma signal using a linear model whose parameters are inferred from neighboring reconstructed luma and chroma samples. Although this mode presents very good coding efficiency, it is observed that ill cases in the linear parameters calculation can be detected and fixed. This paper gives an overview of the LM mode and presents a novel model correction scheme to detect and correct those ill cases. Simulation results show significant bit-rate savings by the proposed correction scheme with limited added complexity.