Bi-Predictive Intra Block Copy for Enhanced Video Coding Beyond VVC

Intra block copy (IBC), an intra coding tool with a single block vector (BV), has been exploited for significant coding gains of screen content (SC) in advanced video coding standards such as VVC. Several studies have applied IBC to camera-captured content (CC), such as the IBC with fractional-sample-precision BV, which was adopted into the reference software for exploring beyond VVC, i.e., the enhanced compression model (ECM). However, there is room to further achieve the coding gains of IBC because all the conventional methods are uni-predictive IBC with a single BV to generate prediction samples. This paper proposes a bi-predictive IBC using two BVs as a new IBC algorithm for CC and SC, realized by extending the number of BVs in BV storage. In addition, this paper proposes encoder early terminations of applying IBC for CC by comparing coefficients and distortions of the IBC and intra prediction to avoid encoder runtime increases while maintaining coding gains. Experimental results show that the proposed method brings $0.15 \%$ and $0.30 \%$ coding gains for CC and SC over ECM-9 under all-intra configuration, with negligible complexity increases. The proposed method has been adopted into ECM-10.