The Fast Coding Block Adaptive Mode Selection Algorithm Optimization In H.264 Standard

Compared with previous standards,at the same quality of coding,H.264 can save around 50%of the bit rate,coding efficiency can doubled than H.263.However,the high coding compression rate uses the high computational complexity for the price.At the same coding quality,its computational complexity is about 3 times of H.263,so its algorithms must be optimized in practical applications to reduce its computational complexity.This mainly because of the introduction of radio distortion optimization strategy and traverse all of the coding modes.Although the many candidate modes can effectively improve the block matching efficiency,improve image quality,lower coding bit rate,but the judgement and selection of all modes greatly increased the computational complexity and increased the coding delay,and should not be implemented effectively at a lot of hardware devices.So,the optimization selection for many candidate modes can reduce the calculation complexity of H.264。The optimization in this article is mainly based on fast algorithm of block mode selection,the major works are as follows.First of all,it introduced the hot technology of H.264/AVC and development actuality at home and abroad,and analysed the inadequacy of H.264/AVC encoder,it has been optimized in the fast algorithm of the H.264 encoder.We analysed the complexity of coding block mode selection,and statisticed the probability of every coding mode which based on CBP residual value.From this it can obtainned that the big coding block mode occupying a considerable proportion.So it can use of the CBP, MVD information of residue to identify relevance of intra and inter image,only calculating radio distortion optimization value of partial mode,and adopting adaptive judgment strategy to filter partial coding mode,optimizing encoder of basic grade, then a fast coding block mode selection algorithm based on RDO is proposed. Experimental results show that under the cost that bit rate increased 3.97 percent, encoding speed increases 60.44 percent in average,and the image peak signal to noise ratio improves 0.015 dB in average.Then analysing the macroblock number of each coding block mode which be used according to threshold and judgment criterion.Effectively selecting coding block mode of current block according to previous coded frame and coded block,it can reduce the rate of misjustice by using single threshold or judgment criterion. Experimental results show that under the premise of assurance image quality effectivly,the bit rate only increases 0.41 percent in average,encoding speed improves 50.40 percent in average.