A fixed-complexity HEVC inter mode filtering algorithm based on distribution of IME-FME cost ratio

Motion Estimation (ME) is a key performance bottleneck of H.265/HEVC encoding. In implementing ME, a fixed or bounded complexity is often desired for efficient pipelining and parallelism. We present a fixed-complexity mode filtering algorithm to reduce the complexity of fractional ME (FME). Firstly, a layer filtering is applied to select the mode candidates. Secondly, the ratio of integer-fractional ME costs (R_f/i) is defined and the confidence interval of R_f/i is utilized for further mode selection. Finally, an algorithm to fix the complexity is applied. Experimental results show that the FME encoding time is reduced by 83.3% with slightly BD-rate increase.