Sample-based Weighted Prediction with Directional Template Matching for HEVC lossless coding

The recently introduced High Efficiency Video Coding (HEVC) standard is currently further investigated for potential use in professional applications. The considered Range Extensions should on the one hand introduce higher bit depths and additional color formats, and on the other hand the coding efficiency of HEVC for high fidelity compression as well as lossless compression is to be improved. In this paper we investigate and improve the recently introduced Sample-based Weighted Prediction (SWP) for HEVC lossless coding. Although being very efficient for natural video content, the SWP algorithm can be further improved for screen content by using a directional template predictor in cases where the SWP algorithm yields worse prediction. The mainly introduced predictor improves the lossless coding results by up to 9.9% compared to the unmodified HEVC reference software for lossless compression.