Improved intra boundary filters for HEVC

This paper presents a group of novel intra boundary filters to refine the intra prediction blocks. The existing intra boundary filters only adjust prediction blocks for a few special intra modes. While the proposed method extends the boundary filtering to all intra modes, and allows to modify up to 6 rows and columns at the boundaries of intra prediction blocks. A group of filters are designed by comprehensively considering the spatial similarity between reference samples and predicted pixels, as well as the statistical characters of boundary prediction distortion. In addition, low computational complexity is also essential to make the proposed filters simple and effective. By involving the proposed boundary filters to revise the intra prediction blocks, better prediction results can be achieved. The proposed method is implemented on top of the H.265/HEVC reference software (HM-16.12), and the experimental results show that 1.0% (up to 1.5%) BD-rate reduction is achieved under All Intra (AI) configuration.