video synopsis is an effective technique to provide a compact representation of the original video by removing spatiotemporal redundancies and by preserving the essential activities. most current approaches for video synopsis will cause collisions among objects, especially when the video is condensed much. in this paper, we present an approach for video synopsis to reduce the collisions. our approach first shifts active objects along the time axis to compact the original video. then, the sizes of the objects are reduced when collisions occur. meanwhile, the geometric centroids of the objects will be kept unchanged to preserve the location information. our contributions are threefold. first, an approach is proposed to decrease collisions in the synopsis video through reducing the sizes of the objects. second, an optimization framework is developed to indicate the optimal time position and the appropriate reduction coefficient for each object. finally, some metrics are proposed, and several experiments are carried out to evaluate the proposed approach. the experiments have demonstrated that the synopsis video produced by our approach has much fewer collisions while the compression ratio is high.