A Fast Fractional-Pel Motion Estimation using 4-Tap Chroma Interpolation Filter for HEVC Encoder Sungjei Kim, Jinwoo Jeong, Sang-hyo Park and Yong-Hwan Kim Korea Electronics Technology Institute (KETI), Seongnam-si, Republic of Korea, {sungjei.kim, jw.jeong, sanghyo.park and yonghwan}@keti.re.kr Abstract. In this paper, we propose a fast motion estimation technique using chroma interpolation filter for High Efficiency Video Coding (HEVC) encoder. In order to reduce the computation time of motion estimation process, the proposed method utilizes 4-tap chroma interpolation filter for motion estimation and 8-tap luma interpolation filter for motion compensation, separately, instead of applying the same 8-tap luma interpolation filter to both motion estimation and motion compensation process. From the experimental results, the proposed algorithm achieves 4.63% time-saving with 0.06% BD-bitrate increase on average, compared to x265 encoder, which is the most computationally efficient HEVC encoder in the industrial field. Keywords: Fast motion estimation, Chroma interpolation filter, and High Efficiency Video Coding (HEVC) 1 Introduction In spite of the superior coding efficiency of HEVC [1] compared to the previous standard H.264/AVC, the computational complexity is still heavy-burden in the real- time application scenario. Especially, the introduction of 8-tap luma interpolation filter for fractional-pel motion estimation and motion compensation in HEVC not only contributes to the coding efficiency but also increases the computational complexity. In the literature, in order to reduce the computational complexity of motion estimation, many fast algorithms have been proposed by reducing the number of search points with spatial-temporal motion correlation and estimating the fractional- pel position without the interpolation [2-5]. However, compared to H.264/AVC standard, the computational complexity of the HEVC’s fractional-pel interpolation method has increased approximately twice in terms of memory access and arithmetic operations [6]. As the complexity of the interpolation computation increases, it has become increasingly important to reduce the complexity of the interpolation itself. In this paper, to reduce the computational complexity of the interpolation itself, we propose a new interpolation filter applying methodology for the HEVC encoder. Because the motion estimation method is not defined at the specification, the encoder Advanced Science and Technology Letters Vol.146 (FGCN 2017), pp.23-29 http://dx.doi.org/10.14257/astl.2017.146.05 ISSN: 2287-1233 ASTL Copyright © 2017 SERSC