运动估计是视频压缩中最重要的环节.H.264编码器由于采用了高精度运动矢量,计算量迅速增长,运动估计消耗整个编码时间80%左右.本文在分析UMHexagonS算法的基础上,分别对UMHexagonS算法中搜索窗口大小的选择、大六边形搜索和小六边形(小钻石)搜索模式三方面做了优化,在保持了原有图象质量的情况下有效的节省了运动估计时间.通过对各种测试序列的实验证明,优化后的算法与UMHexagonS算法相比,在重建图象质量和码率接近的情况下,运动估计时间平均节省了18.292%,降低了算法的复杂度,提高了编码器的实时性.%Motion estimation (ME) is vital to video compression. Due to the adoption of the high precision of motion vector (MV) in H.264 encoder, me computational cost increases rapidly, and ME takes almost 80% encoding time. In this paper, based on the UMHexagonS algorithm,an optimized algorithm is proposed based on the dynamic search range selection,big hexagon and small hexagon search mode respectively, which saves ME time effectively without quality loss. Experimenting with some typical video sequences proves that,compared to UMHexagonS algorithm,our optimized algorithm can save about 18.292% ME time and reduce the complexity of original scheme as well as enhance the real-time performance of the encoder but almost has no change in the reconstructed picture quality and bitrate.
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