Unified Intra Mode Coding Based on Short and Long Range Correlations

There has been a consensus regarding the intra prediction technique in video coding that the spatial redundancy can be efficiently removed by the locally accessible reference samples with certain projections and interpolations. In this paper, we revisit the short and long range correlations of the image content in the context of video coding, and it is interesting to find that the natural scene videos exhibit substantially different characteristics from screen content videos. This motivates us to redesign the intra mode coding method based on both short and long range correlations, as the existing approaches based on local content correlations cannot always effectively capture the most probable mode. One key feature of the proposed method is that it achieves unified content adaptive coding and is applicable across different video content. Experimental results on the versatile video coding (VVC) platform VTM-3.0 show the effectiveness of the proposed approach, leading to 3.73% bit rate savings for screen content videos and 0.10% bit rate savings for natural scene videos under all intra configuration.