Low complexity SAO in HEVC base on class combination, pre-decision and merge separation

High efficiency video coding (HEVC) is the most recent video compression standard that doubled the coding efficiency as compared to the predecessor H.264/AVC. HEVC adopts sample adaptive offset (SAO) right after deblock filtering process. According to the intensity and the edge property, the encoder classifies the reconstructed pixels into different categories, and assigns one offset for each category of pixels. This paper proposes class combination, pre-decision and merge separation to decrease the sao processing time. Class combination combines the four edge offset (EO) type into one. Pre-decision decreases the band offset (BO) search time from 29 to 4. Merge separation limits the merge range to saving the efficiency loss. Experimental result shows the proposed methods can saving about 38% SAO processing time with little degradation (BD-bitrate increased by 0.16% and ΔPSNR decreased by 0.001) in terms of coding gain.