Research And Design Of Video Segmentation & Motion Estimation Based On MPEG-4

With the user's increasing demand on video information, H.26X, MPEG seriesvideo standards have been established. Our country has been working in our own videostandard which is called AVS and in which the video part has been published in March2006．MPEG-4 is a video compression standard which has content-based functionalitiesand plays an important role in the Video Monitor, Video Retrieval, IPTV etc. Based onthe MPEG-4 standard, this paper does a deep research on video compression and designtwo parts of MPEG-4--video segmentation and motion estimation.Although MPEG-4 defines "Video Object (VO)", the concrete method of VOsegmentation hasn't been explained, which becomes the topic investigated. First, thispaper introduces and analyses some video segmentation methods. Among these methods,the symmetrical differencing can extracted objects quickly and veraciously. But thismethod has a problem that it can't detect objects integrally and even can't detect objectssometimes. So, this paper presents a video segmentation method based on symmetricaldifferencing combined with motion estimation. Meanwhile, the adaptivedouble-threshold method is used to fill the holes due to noise and objects moving. Theresult of the experiment demonstrates that the presented algorithms can resolve theproblem in symmetrical differencing.Motion Estimation (ME) is an important part not only in the video segmentationpresented in this paper but also in most video encoding systems, since it cansignificantly affect the speed and output quality of an encoded sequence. Firstly thispaper summarizes the principle of motion estimation briefly. Then describes andanalyses some classic motion estimation algorithms.Based on the study of the video sequences, we find that the motion vectordistribution not only has a characteristic of zero biased but also has anothercharacteristic that the distribution is more dense in the cross shape with (0, 0) positionas the center. According to the characteristic, this paper presents a new cross searchalgorithm (NCS) using big and small cross pattern instead of diamond patterns. Theresult of the experiment demonstrates that the NCS manages a significantlyimprovement versus DS in both terms of quality of video and speed.Besides the search algorithm, the initial search point prediction is very important in motion estimation. Therefore a prediction algorithm is designed for NCS that presentedin this paper above. First, this paper reduces the predictors to two, and then it decideswhat to do next step in accordance with the prediction result: whether enter the differentpattern of motion estimation or finish the motion estimation.