Fast parameter estimation algorithm for sample adaptive offset in HEVC encoder

HEVC has adopted Sample Adaptive Offset (SAO) as a new in-loop filtering block. SAO can significantly improve coding efficiency, however, it requires exhaustive operations in order to calculate best SAO parameters for each Coding Tree Unit (CTU). SAO parameters estimation process takes around 93 % of the overall SAO execution time which depends on number of candidate SAO modes. Real time and low power video encoders are in demand for more efficient SAO encoding algorithms. In this paper, we propose an algorithm that reduces the SAO parameter estimation complexity by adaptively reusing the dominate mode of corresponding set of CTUs. The proposed algorithm can save up to 75% of SAO parameter estimation time with only 0.8% BD-rate penalty.