Abstract: H.264/AVC achieves high coding efficiency due to utilizing the full mode decision based on Rate-Distortion Optimization technique（RDO），which brings about tremendous computational complexity.To overcome it，JVT reference software proposes a new fast mode decision algorithm.In this paper，this new algorithm is introduced in detail.Some improved schemes are proposed based on the study and analysis of the advantages of the NFMD，such as early predict the mode of current macroblock，introduce timing terminate criterion，fast intra mode selection determination.Experimental results show that the improved strategies can reduce about 35%~55% of encoding time and 45%~60% of motion estimation time，while the R-D performance and bit rate are almost same as original algorithm.

Key words: H.264/AVC, inter-frame prediction, mode decision, spatio-temporal correlation

摘要： 针对H.264 运用基于率失真优化的全模式搜索技术，带来的模式选择异常复杂的计算，JVT提出了一种新的快速模式选择算法（简化为NFMD）。介绍了该新算法，对其综合性能的优越性进行了初步研究和分析，并提出了改进策略，如早期预测当前宏块编码模式、引入适时终止模式选择策略、快速帧内模式选择判断。实验结果表明，改进的策略能减少NFMD算法35%~55%的编码时间和45%~60%的运动估计时间，而码率和率失真性能的变化可以忽略不计。

关键词: H.264/AVC, 帧间预测, 模式选择, 时空域相关性