A fast intra mode selection method for H.264 high profile

This paper proposes a fast intra mode selection method for high profile of H.264/MPEG-4 AVC. H.264 high profile supports three intra modes: intra_4x4, intra_8x8 and intra_16xl6. There are nine possible prediction directions for intra_4x4 and intra_8x8, and four for intra_16xl6. For intra_4x4, the proposed method checks all the nine possible prediction directions and determines a best direction per 4x4 block within a macroblock (MB). For intra_8x8, it only checks the prediction directions selected for the four 4x4 blocks of an 8x8 block within a MB plus the most probable mode (MPM). The saving in selecting a prediction direction for intra_8x8 can range from 45% to 100%. Further, if the four 8x8 blocks within a MB have different prediction directions, the MB is considered inhomogeneous. Tests over ten SD sequences indicated about up to 15% inhomogeneous MBs. For those inhomogeneous MBs, the prediction direction checking for intra_16xl6 is skipped. For homogeneous MBs, the four possible prediction directions for intra_16xl6 will be further evaluated. Simulation results showed that the proposed method does not bring any performance degradation with these complexities reduction.