Fast feature-based mode decision for 4×4 intra prediction in H.264/AVC

Abstract

Intra coding in H.264/AVC can significantly improve the compression efficiency at the cost of high computational complexity due to the use of the rate-distortion optimization technique. To reduce the complexity of intra prediction, we propose a feature-based mode decision algorithm for 4×4 intra prediction. This algorithm is motivated by the fact that a good prediction mode usually has a small residue block, which is the difference between the original block and predicted block. The sum of the absolute transformed coefficients and deviation information of residue block are used to measure the distortion of prediction mode and the smoothness of residue block, respectively. According to the ranking of these two features of all possible modes, and together with the most probable mode, small numbers of candidate modes can be determined. Moreover, the candidate modes are further reduced to only one by using two early termination rules based on the correlation of rank and most probable mode. Simulation results demonstrate that the proposed mode decision method reduces about 60% of total encoding time of intra coding with negligible loss of coding performance.