A novel angle-restricted test zone search algorithm for performance improvement of HEVC

High Efficiency Video Coding (HEVC) is the latest video encoding standard and has approximately 50% bit-rate saving compared to its predecessor. However, the motion estimation (ME) is considerably complicated by the incorporation of varieties of partitioning modes and a quad-tree based coding structure, and also by increasing the basic coding unit size by a factor of 16. Motion estimation is the most complex task in the video encoding process, consuming 60-80% of overall encoding time. This paper proposes a new algorithm, angle-restricted test zone (ARTZ) for motion estimation which is based on a test zone (TZ) search, exploiting directional probabilities of motion vector search. In our experiments, this proposal achieves a time saving in motion estimation of about 20% to 50% compared to a TZ search in the HEVC test model (HM) implementation for UHD videos without significant degradation of PSNR.