Abstract: H.264/AVC uses the rate distortion optimization method to determine the best mode for a macroblock （MB） to improve coding efficiency. But it increases computational complexity. To overcome this shortcoming, a fast intra mode decision algorithm for H.264 is raised. In chroma prediction, four prediction modes can be reduced into one or two modes according to the textural features of a MB. In luma 16×16 prediction, the mode which has lowest Sum of Absolute Transformed Difference（SATD） can be selected as the best prediction mode. In luma 4×4 prediction, the algorithm chooses three probable modes from nine modes as the candidate modes. Comparing the total cost of sixteen 4×4 blocks and one 16×16 block, the best block size can be determined. Experimental results show that the coding time of the propose method is decrease about 68% while maintaining similar PSNR and bit rate performance of H.264 intra encoding.

Key words: H.264/AVC, intra prediction, mode select

摘要： H.264/AVC视频编码标准中用率失真优化（RDO）方法为一个宏块（MB）判决最佳编码模式来提高编码效果，加大了算法复杂度并且计算冗余大。为了克服这一缺点，一种快速帧内预测模式选择算法被提出。在色度预测中，根据宏块的色度纹理复杂度，把原先的4种模式降到1或2种；在亮度16×16块模式判决中，根据最小哈达玛变换的绝对误差和（SATD）来选择最佳模式；在亮度4×4块模式判决中，该算法在9种模式中选择3种可能模式作为候选模式。通过比较16个4×4块总代价与1个16×16块的代价来选择最佳块选择模式，实验表明，该算法能在节省69%左右编码时间的情况下，比特率与峰值信噪比（PSNR）保持不变。

关键词: H.264/AVC, 帧内预测, 模式选择