Film Grain Regions characteristics SEI message

The film grain characteristics (FGC) Supplemental Enhancement Information (SEI) message was developed in 2003 and was incorporated into the H.264/AVC specification then ported into the HEVC, VVC and Versatile supplemental enhancement information (VSEI) specifications. The FGC SEI message is used to signal and convey to video decoders metadata characterizing a film grain signal, that can be synthetized and superposed to the decoded video as a post-decoding process. It is an efficient solution to mimic the native film grain present in the input video that may have been removed by the encoding, enabling artistic intent preservation. It is also considered as an efficient solution to bring perceptual quality improvements by mitigating visual artefacts resulting from the coding process. The FGC SEI message parameters relate to the entire picture and do not allow a fine local control of the film grain. This paper describes the Film Grain Regions characteristics (FGR) SEI message, submitted as a candidate new VSEI SEI message, that enhances the FGC SEI by adding region-based control parameters enabling to adjust the synthesized film grain per region. After introducing the syntax and semantics of the FGC SEI message, the paper describes the additional features brought by the FGR SEI message. The region-based grain adaptation is showcased on different use cases that illustrate the potential benefits of the technology.