Joint inter-intra prediction based on mode-variant and edge-directed weighting approaches in video coding
Most modern video compression codecs, like VP9, HEVC and H.264, encode square or rectangular blocks either by inter prediction or intra prediction. A joint inter-intra predictor that combines motion compensation and intra extrapolation by two novel weighting schemes is proposed to improve compression quality. Prior work on joint prediction employs inter-intra weights that only rely on the pixel locations. As an enhancement, we design a weighting approach by also considering the angle of intra prediction, which is the actual direction that the intra prediction errors evolve. Moreover, our second approach, inspired by prior work on geometric-partition-based motion compensation, breaks the limitation of traditional quad-tree partition by jointly using different predictors that implies soft step weighting functions for new and existing objects co-occurring around irregular motion edges. The proposed joint prediction approaches deliver consistent coding gains, as shown by extensive experiments on the experimental branch of VP9, Google's open source video compression tool.