Fast Motion Estimation in HEVC Inter Coding: An Overview of Recent Advances

High Efficiency Video Coding (HEVC), the latest video coding standard, is becoming popular due to its excellent coding performance, in particular in the case of high-resolution video applications. However, the significant gain in performance is achieved at the cost of substantially higher encoding complexity than its precedent H.264/AVC, in which motion estimation (ME) is one of the most time-consuming parts that effectively removes temporal redundancy. During the development, especially after the release of H.265/HEVC, plenty of fast ME algorithms have been developed to reduce the motion estimation complexity for better application of HEVC into practical real-time video applications. In this review, we provide a comprehensive review of the state-of-the-art fast ME algorithms for HEVC inter coding, for both integer-pixel and fractional-pixel ME algorithms. In all, this review paper provides a comprehensive review of the recent advances of ME for HEVC inter frame coding and hopefully it may provide valuable leads for the improvement, implementation and applications of HEVC inter-prediction as well as for the ongoing development of the next generation video coding standard.