For example, the object is composed of four blocks, i. e. block A, B, C, D. Block A locates the left of block B and above block C. According to order, its code is ABDC etc. This code does not change its order after the object rotates, zoom, downsizes. The disadvantage of this method is that it will lose the target when the color is changed. A video fluid is composed of compressed data which include I, P and B(bi-prediction) frame. The data of each block of P frame is predicted by motion prediction and compensation from the data and motion vector of I frame.
MPEG视频流由I、P、B组成，为减少空间、时间的冗余，P帧的数据来自已经解压缩的I帧和P帧，B帧的数据来自已经解压缩的I帧和P帧或者P帧和P帧，这些需要解码的图像通过运动预测和补偿对P帧／B帧进行解码，P帧／B帧中每一个宏块的数据来自于最佳匹配的相应I帧和P帧或者P帧和P帧中，以及图像变化而必须的运动补偿。