H.264中UMHexagonS运动估计算法的改进

针对H.264中UMHexagonS算法进行研究,提出了改进的快速运动估计算法。首先对UMHexagonS算法中的固定搜索窗口、非对称十字搜索、5×5的小矩形螺旋搜索、非均匀多层次六边形格点搜索和扩展的六边形搜索进行研究;然后提出了相应的减少搜索点数的优化算法,这些优化算法分别称作动态搜索窗口、自适应十字模型搜索、方向性的3×3小矩形搜索、基于预测方向的密集搜索和改进的扩展六边形搜索,这些优化算法形成了自适应模型方向搜索(APDS)算法。对各种类型的测试序列进行实验,与UMHexagonS算法相比,结果表明APDS算法在重建视频质量和码率基本相当的条件下,运动估计时间平均减少了29.64%,每形成一个运动矢量平均节省搜索了21.64个点数；

Improvement of UMHexagonS motion estimation algorithm in H.264

The UMHexagonS motion estimation algorithm in H.264 was studied, and an improved fast motion estimation algorithm was proposed. First, the fixed search range, the unsymmetrical cross search, the 5×5 small rectangular spiral search, the uneven multi-hexagon-grid search and the extended hexagon-based search were analyzed. Then the optimized search modes were given respectively, which called dynamic search window, adaptive rood pattern search, the directional 3×3 small rectangular search pattern, the predictive intensive direction search and the modified extended hexagon-based search. Thus Adaptive Pattern Direction Search (APDS) algorithm was formed by these optimized search modes. The experimental results conducted on different test sequences show that, compared to UMHexagonS algorithm, the APDS algorithm can save about 29.64% Motion Estimation (ME) time and reduce the average number of checking points per Motion Vector (MV) generation about 21.64, while incurring nothing obvious loss in the reconstructed picture quality and less increment in the bit rate. With the efficiency improvement of ME, the real-time performance of the encoder is further enhanced.