Fast three step intra prediction algorithm for 4×4 blocks in H.264

This paper presents a fast three step algorithm for H.264 4×4 intra prediction. Motivated by the high correlation of RD cost between different prediction directions, in each step of the algorithm, the proposed algorithm efficiently explores the neighborhood direction around the minimum one and thus skips other unlikely ones. Thus, the proposed algorithm can complete 4×4 intra prediction by only examining 6 modes instead of 9 modes in the full search algorithm. The simulation result shows that the proposed algorithm can maintain a similar PSNR quality to the full search algorithm with only about 1% bit-rate increase.