Fast template matching for intra prediction

Intra prediction is an important step in video coding, where spatial redundancy is exploited for coding efficiency. The state-of-the-art H.265/High Efficiency Video Coding (HEVC) standard provides 35 intra prediction modes including 33 angular modes and a DC as well as a Planar mode. Although these intra prediction methods are quite efficient, there is still room for improvements, especially when complex image structures are involved. Template matching was proposed previously for H.264/Advanced Video Coding (AVC) with up to 11% BD-rate gain. However substantial decoder complexity increase from the implied search algorithm makes it less attractive for practical applications. In this paper, we propose a fast template matching intra mode for HEVC. The proposed mode is scalable in the sense of providing different trade-offs between decoder complexity and BD-rate gains. For a specific choice of parameters, fast template matching mode can achieve an average BD-rate gain of 1.15% with a maximum BD-rate gain of up to 4.6% at a 33% increase in decoder run-time. Overall, fast template matching can provide the same coding gain as conventional template matching approaches, but with significantly less decoder complexity.