Fast VVC Intra Subpartition based on Position of Reference Pixels

Intra Subpartition (ISP) is a coding tool newly introduced to the VVC (Versatile Video Coding) standard. It splits a luma block vertically or horizontally into equal-sized sub-partitions and encodes the sub-partitions one by one sequentially using the same intra mode. In order to minimize the encoding complexity of the ISP tool, we investigate a method of skipping a selected ISP mode from the rate-distortion optimization (RDO)-based ISP mode search process based on the position of reference pixels. Our proposed fast ISP search method reduces the average total encoding time by 4% with a bit rate increase of 0.04% under all intra coding configuration.