帧间块模式选择是H.264视频编码器中比较耗时的模块之一，为降低H.264视频编码器帧间模式选择的复杂度，提出了一种利用宏块的时空相关性实现帧间模式快速选择的方法。该算法通过对视频序列连续帧的时间相关性和相邻宏块的空间相关性进行统计、分析，首先得到宏块模式转换的统计分布规律，并根据此规律得到宏块的初始候选模式；然后利用基于主宏块的宏块跟踪，找到最相关宏块，再由率失真门限筛选出最佳编码模式。仿真实验结果表明，该快速模式选择算法可以在保证视频编码质量的同时，很大程度上降低了编码器的计算复杂度，平均节省编码时间约64%，平均信噪比下降约0.31 dB。

Inter-mode decision is one of the time-consuming units in H.264 encoder.To reduce the complexity of the block mode decision process，an inter-mode decision algorithm based on spatiotemporal correlation of macro-block was proposed.First，the property of temporal correlation in successive frames and spatial correlation in neighboring macro-block is analyzed，and statistical results for the MB mode change is summarized.According to these characteristics，original candidate modes are chosen.Second，with macro-block tracking of the main macro-block，the most correlated macro-block is found.Then the best coding mode is chosen with a threshold of rate distortion.The results of simulation test show that the proposed fast mode decision strategy can highly improve the efficiency of real time H.264 encoder while maintaining video coding quality.The method can save the encoding time up to 64% on average with －0.31dB performance degradation.