High-Order Intra Prediction for Future Video Coding

Intra prediction acts a significant role in removing the spatial redundancy in the hybrid coding framework. Versatile Video Coding (VVC) employs a set of angular intra modes to generate directional contents based on the linear projection hypothesis. However, the linear based predictor is not expressive enough for generating high-fidelity patterns with non-linear structure. To compensate for that, we propose a high-order intra prediction (HOIP) for future video coding in this paper. In particular, the HOIP is modeled by a quadratic extrapolation function. To be compatible with the present intra prediction mechanism, the quadratic function can be formulated by two angular intra modes. To reduce the encoding complexity, we further propose a search pruning strategy to find the most appropriate pair-wise modes, and it can be flexibly extended for higher coding performance. The extensive experimental results demonstrate the effectiveness of the proposed method. Up to 0.6% BD-rate saving is obtained with the moderate complexity increment.