Improvement on Intra Block Copy in Video Coding with Reference Block Recompression

Intra Block Copy is a tool adopted in HEVC and VVC extensions on SCC, it significantly improves the coding efficiency of screen content materials. To reduce memory consumption and decoder complexity, the reference region of IBC in VVC is limited. In this paper, we propose a method that recompresses the reference block of IBC, so that more reference blocks can be stored while using the same memory space. This allows IBC to expand its search range and results in BD-rate reduction. The proposed method includes spatial prediction, variable length coding, quantization, and two methods to realize the IBC buffer with recompressed reference block. We test these two methods in the reference software of VVC and achieve BD-rate reduction of 1.8% and 4.0% on average respectively for TGM test sequences.