Intra block copy in Versatile Video Coding with Reference Sample Memory Reuse

Screen contents such as online gaming streaming, remote desktop and WIFI display, become popular in current mainstream video applications. In versatile video coding (VVC), the most recent international video coding standard development, coding tools have been evaluated for optimizing screen content materials. Intra block copy (IBC) has shown its effectiveness in coding of computer-generated contents such as texts and graphics. Therefore, it has been previously included into the HEVC standard version 4, extensions for screen content coding (SCC). A constrained version of IBC mode has also been adopted in the VVC standard where the compensation range is limited within the current coding-tree unit (CTU), assuming a 1-CTU size of memory is allocated for storing IBC’s reference samples. In this paper, methods are proposed to efficiently utilize this reference sample memory for IBC mode such that effectively the search range for IBC mode can be increased without requiring more memory to store the reference samples. As a result, significant coding efficiency improvement over the traditional 1-CTU search range setting can be achieved. One of the proposed memory reuse strategies is considered practical for implementation and therefore has been included in the VVC standard.