Abstract: In order to gain the optimal mode, H.264 adopts Rate Distortion Optimization (RDO) technique to compute the cost of every mode for each macroblock, but it increases computational complexity. A precision mode selection algorithm in fast frame was proposed which combined PAN algorithm proposed by Pan. Firstly, the intra predictions type were decided by whether a macroblock was smooth. Secondly, the PAN algorithm was improved and a new algorithm based on the statistical properties of adjacent blocks was proposed. The experimental results show that the method mentioned in this paper reduces the total encoding time with negligible loss in Peak SignaltoNoise Ratio (PSNR) and a slightly increased bitrate, compared with full search algorithm and PAN algorithm.

Key words: intra prediction, mode selection, H.264

摘要： 为了得到最优模式，H.264采用了率失真优化(RDO)技术计算宏块的每种模式的代价，但是这样增加了计算复杂度。结合PAN算法提出了一种快速帧内预测模式选择算法，首先根据宏块是否平坦决定帧内预测的类型——帧内4×4和帧内16×16。其次，改进了PAN算法，提出了一种快速帧内预测模式选择的新算法。实验结果表明，新算法与全搜索算法和PAN算法相比，减少了编码时间，峰值信噪比(PSNR)基本保持不变，输出码率略有增加。

关键词: 帧内预测, 模式选择, H.264