JVET-L0279 CE3-related: Unification of angular intra prediction for square and non-square blocks [L. Zhao, X. Zhao, S. Liu, X. Li (Tencent)]
In this contribution, two modifications are proposed to unify the angular intra prediction for square and non-square blocks. Firstly, angular prediction directions are slightly modified to cover diagonal directions of all block shapes. Secondly, it is proposed to keep all angular directions within the range between bottom-left diagonal direction and top-right diagonal direction for all block sizes. Simulation results reportedly show that, with almost no impact on the encoder or decoder run-time, average -0.06% BD-rate gain is achieved on top of VTM2.0.1 under all intra (AI) configuration.
Several experts who are familiar with wide-angle modes (including companies who originally proposed it) expressed that this is a beneficial simplification and clean design.
It is also confirmed that there is no change to the reference lines that are used, and that it is also compatible with multi-line intra prediction that was adopted in CE3.
Decision: Adopt JVET-L0279.