Macroblock mode decision scheme for fast encoding in H.264/AVC

Abstract

To improve coding efficiency, the H.264/AVC video coding standard uses new coding tools, such as variable block size, quarter-pixel-accuracy motion estimation, multiple reference frames, intra prediction and a loop filter. Using these coding tools, H.264/AVC achieves significant improvement in coding efficiency compared with existing standards. However, the encoder complexity also increases tremendously. Among the tools, macroblock mode decision and motion estimation contribute most to total encoder complexity. This paper focuses on complexity reduction in macroblock mode decision. Of the macroblock modes which can be selected, inter8×8 and intra4×4 have the highest complexity. We propose three methods for complexity reduction, one for intra4×4 in intra-frames, one for inter8×8 in inter-frames, and one for intra4×4 in inter-frames. Simulation results show that the proposed methods save about 56.5% of total encoding time compared with the H.264/AVC reference implementation.