A novel strategy for video object segmentation in normal video frames, which is an indispensable preprocessing of the object based video encoding in the MPEG-4 standard, is presented. It is a semi-automatic strategy, which combines the efficiency (speed) of automatic segmentation and the accuracy of manual segmentation. Initially, the object contour in the first frame is specified interactively by a user using a computer-aided tool based on our improved Intelligent Scissors. The frames following then undergo an automatic region-based object tracking process. A user interface is designed to display the object tracking result and allow the user to observe it during the tracking process. The user can suspend the process when the result is considered inaccurate or unacceptable, and interactively correct the object contour in the first frame containing the unacceptable result with the proposed computer-aided tool. The automatic region-based tracking process can then be resumed with the corrected object contour as the new initial object contour. This tracking-correcting cycle can be repeated until the end of the video clip is reached.