Research Of The Search Algorithm In Motion Estimation And The Realization Of DSP

Motion estimation search algorithm is the basis of inter encode, and the commonly motion estimation search algorithm adopts the best SAD matched point to carry through the block match in the search area in order to obtain the motion vector of the block. The different search methods adopt different search strategies in the search of the best SAD. It provides Full Search,Three Step Search,New Three Step Search,Diamond Search in H.264 standard, but all of these algorithms exist the problem which the search speed doesn't match the precision; meanwhile, there is promotion space both at search precision and speed in the specifical video frequency.The main research and work of this paper include several aspects as follows:(1)Analyze Full Search, Three Step Search, New Three Step Search, Four Step Search, Cross Search Algorithm, and Diamond Search and carry on the simulation. The simulation result confirms that Diamond algorithm has the relatively good performance in the several basic search algorithms at present.(2) Study the directional diamond algorithm on the basis of diamond algorithm, and we know that the directional diamond search algorithm reduces search points through adopting horizontal and vertical plate to replace the big and small plate of diamond algorithm, but this algorithm will leak some point. Aiming at this problem, this paper proposed an improved directional diamond search algorithm. It adopts the threshold value and uses different search plates to carry on motion estimation through predicting the motion types of the macro block, when the block is slow, we use small diamond plate, if not, we use directional diamond plate. Comparing with the directional diamond algorithm, the experiment shows that, this method can eliminate the phenomenon of leaking points and improve the search precision when most of the blocks are slow in the video frequency; meanwhile, it also can reduce search points and improve the speed.(3)Realize the improved directional diamond algorithm in this paper on the platform of TI DM642. Through setting probe to load the standard video sequence data into DSP buffer, dispose the data in the buffer, and realize the improved directional diamond algorithm. Aiming at the real-time appeal of H.264, this paper makes a lot of optimization to DSP soft program in order to insure the search algorithm fulfill the time appeal of H.264.Comparing with the traditional search algorithms, the improved directional diamond algorithm has a better promotion at the search speed and precision, is easy to realize on DSP, and has certain application value.