Enhanced Intra Prediction Mode Coding by using Reference Samples

HEVC utilizes 35 intra prediction modes to predict each luma block. To ensure the selected mode for a luma block is signaled with minimal overhead, HEVC defines a set of three most probable modes (MPM), which are derived based on the modes of its two neighbors. If the intra prediction mode is not one of these three most probable modes, it is coded as one of the remaining modes using a longer codeword. To improve the efficiency of intra prediction mode coding further, this paper presents a method to derive a second set of most probable modes, by using neighboring reconstructed samples. One line of reference samples is used as the original pixels and predicted by another line of reference samples. The sum of absolute differences (SAD) is employed as a measurement to select several modes with minimum SADs as the second MPM set. Experimental results show that for all intra configurations, the proposed method achieves on average 0.54%, 0.34%, and 0.34% BD-rate reductions for Y, U and V, respectively.