motionEst4SS

代码说明：

  四步搜索算法对三步算法进行了适当的改进，在一定程度上弥补了TSS算法在估计细小运动时的不足，并加入了半途中止的策略，进一步提高了搜索精度 (Four-step search algorithm for three-step algorithm to improve the appropriate, to a certain extent make up for the TSS algorithm in estimating the inadequacy of a small movement, and joined the mid-suspension strategy to further improve the search accuracy)