基于x264的快速运动估计算法优化

Optimization on Fast Motion Estimation Algorithm Based on x264

运动估计是H.264视频编码标准中最重要且最耗时的一部分,大约占用这个视频编码的60%~80%的时间,针对x264中UMHexagonS快速运动估计算法编码速度的局限性,分别对算法中阈值的选择、提前终止条件判定、大六边形搜索模式三方面做了优化,同时改进COST_MV（）函数,有效地缩短了计算SAD值的时间。通过仿真实验表明,优化后的UMHexagonS算法在视频质量（PSNR）下降很小的情况,搜索点数减少了约30%,平均节省了20%~40%整体运动估计时间,提高了编码器的实时性。

Motion estimation is the most important and time consuming part of H.264 video coding,it takes about 60 %~80 % of encoding time.To improve the encoding speed of the UMHexagonS algorithm in x264,an optimized algorithm is proposed via the modified scheme of the threshold selection,early termination of condition and big hexagon search mode.The modified method of the COST_MV（） function is presented to shorten the computing time of SAD value.The simulation experimentation shows that the proposed algorithms can reduce search points by about 30 % with small video quality decline,saves 20 % to 40 % of the estimated time and enhance the real-time performance of the encoder.