Spatial Similarity-Based Fast Mode Decision for VVC Chroma Intra Coding

Haihang Wang, Feng Yuan, Liqian Zhang, Jixing Chen, Fu Lee Wang, Zhaoqing Pan

Abstract: The Versatile Video Coding (VVC) is the latest video coding standard that includes advanced intra coding techniques such as the chroma separate tree and cross-component linear model to improve the prediction accuracy of chroma components. However, these sophisticated techniques inevitably increase the computational complexity of chroma intra coding. In this paper, we propose a fast chroma intra-prediction mode decision algorithm to reduce the computational complexity of the VVC encoder. Firstly, the mode selection correlation between the current chroma Coding Unit (CU) and its nearest-encoded chroma CU is analyzed. Then, based on the variation of the sum of modulus differences, an early mode decision is proposed for the current chroma CU to determine whether the best coding mode should be traversed or directly inherited from its nearest encoded chroma CU. The experimental results show that the proposed algorithm significantly reduces the computational complexity of chroma intra-prediction and achieves an average of 28% chroma intra encoding time saving with only 0.08-1.43% performance degradation in terms of BD-rate.