On Derivation of Most Probable Modes for Intra Prediction in Video Coding

High Efficiency Video Coding (HEVC) standard introduced 35 intra prediction modes in order to improve intra prediction performance. To signal mode of the current block to the decoder a list of three most probable modes (MPM) is derived based on the modes of the two neighboring blocks. Similarly, six MPMs are used in the recent Joint Exploration Model (JEM) to accommodate the increased number to 67 intra prediction modes. One method to achieve this is to use an extension of HEVC approach. The other one employs the modes of the five neighboring blocks, together with their derived modes and default modes, in an ordered MPM candidate list. Our contribution is to use case-based multiple candidate lists. For each defined case, the corresponding list is sorted based on the probability of each candidate. The index of a case is computed based on the defined status values. Experimental results show 0.22%, 0.19%, 0.18% BD rate savings for Y, U, and V components for all-intra configuration, respectively.