在新一代MPEG-4视频编码标准中，为了支持面向对象编码和实现基于内容的应用，视频的半自动分割成为关键技术之一，为此提出了一种基于层次光流的半自动时空视频分割算法。该算法由空域分割和时域分割组成。在空域分割中，提出的基于点的图形用户界面（PBGUI），在用户的协助下，能够精确地定义需要分割的视频对象（VO）。时域分割根据空域分割的结果采用层次光流算法对视频对象进行边界和整体跟踪。实验结果表明，利用该算法，能够精确地分割出视频对象。

In the new MPEG-4 video coding standard, the semi-automatic video segmentation plays a key role in supporting object-oriented coding and enabling content-based functionalities. A novel hierarchy optical flow based semi-automatic spatial-temporal video segmentation method is presented in this paper. The proposed algorithm comprises of spatial and temporal segmentation modules. In the spatial segmentation stage, the user can input points around the video object(VO) with the proposed point-based graphic user interface(PBGUI), then active contour model and tracking bug algorithm are used to precisely define the video object of interest to be segmented. With the result of spatial segmentation, the temporal segmentation involves non-rigid object boundary tracking and rigid object whole entity tracking by hierarchy optical flow algorithm based on the algorithm proposed by Lucas and Kanade. And the tracking points selection algorithm is proposed to greatly improve the tracking performance in the rigid object whole entity tracking. The experimental results show that the proposed algorithm can precisely segment video objects from video clips and can be applied to object-oriented coding, content-based functionality and multimedia database indexing.