为了降低H264中I帧编码模式选择时的计算量，提出了一种快速编码算法。该方法首先选择适当的滤波算子对待编码宏块进行平滑滤波，同时使用滤波后的结果与原始宏块数据进行比较来得到滤波残差量；然后将该滤波残差量作为依据，提前判断出当前宏块编码所属的基本模式集，这样由于减小了候选模式的范围，因而提高了模式决定的效率。在判定过程中还使用了双阈值方法，该方法可确保在作出合理判决时，亦不影响图像质量。采用该算法不仅一定程度上降低了计算复杂度，并且对图像质量的影响可以忽略不计。实验表明，这种新的算法可以降低约16%的计算量，而编码图像峰值信噪比的下降只有01dB，且对比特率的影响不到1%。

To reduce the complexity of I frame mode decision process，a fast mode decision algorithm is proposedA low pass filter is implemented for each macroblock. After the macroblock is smoothed by this filter we compare the result with the original data and generate the difference between themThen the basic candidate mode class is determined based on the difference，so that the number of candidate modes is reducedTherefore this new method can reduce the complexity of mode decision process in H264 coding at a certain degree with almost no influence on the performance and the bitrate. Further experiments indicate that this new method can save about 16% time in computation with 01dB decline of performance，and less than 1% increase on bitrate