Deblocking filtering in VVC

The paper describes the novel aspects of deblocking filter in VVC. We demonstrate the insufficiency of HEVC deblocking filter when employing larger transform block sizes and describe the design changes made to enable reduction of the resulting blocking artifacts for both luma and chroma, while also allowing for parallel friendly processing. Additionally, VVC deblocking includes filtering based on local luma level to address blocking artifacts observed in high dynamic range content. The paper also describes modifications made in VVC deblocking to address blocking artifacts introduced by additional coding tools present in VVC (but not in HEVC). The additional coding tools result in prediction and transform block boundaries at disparate locations in a coded picture. Similar to previous generation of video coding standards, the deblocking in VVC, adaptively filters samples located at the block boundaries based on coding modes and local spatial activity.