Probability-based decoder-side intra mode derivation for VVC

Intra prediction is typically used to exploit the spatial redundancy in video coding. In the latest video coding standard Versatile Video Coding (VVC), 67 intra prediction modes are adopted in intra prediction. The encoder selects the best one from 67 modes and signals it to the decoder. Bits consuming of signaling the selected mode may limit the coding efficiency. To reduce the overhead of signaling the intra prediction mode, a probability-based decoder-side intra mode derivation (P-DIMD) is proposed in this paper. Specifically, an intra prediction mode candidate set is constructed based on the probabilities of intra prediction modes. The probability of an intra prediction mode is mainly estimated in two ways. First, the textures are typically continuous within a local region and intra prediction modes of neighboring blocks are similar to each other. Second, some intra prediction modes are preferable to be used than others. For each intra prediction mode in the constructed candidate set, intra prediction is processed on a template to calculate a cost. The intra prediction mode with the minimum cost is determined as the optimal mode and used in the intra prediction of the current block. Experimental results demonstrate that P-DIMD can achieve 0.56% BD-rate saving on average compared to VTM-11.0 under all intra configuration.