Research On Two-pass Video Coding Optimization Algorithm

The gradual popularization of consumer electronic devices and the various needs of daily life have continuously brought new challenges to video compression technology.Videophone,distance education,telemedicine,live video,digital libraries,interactive video games and so on are all popular.Digital video coding has a history of nearly four decades,but with the development of video demand from high-definition video to ultra-high-definition video such as 4K and 8K,video coding technology is also facing new challenges.How to solve the problem of high-definition video compression,how to ensure the transmission quality of high-definition video under the condition of limited bandwidth,and how to meet the users' demand for the visual quality of high-definition video.These have become the key issues to be solved urgently in the development of video coding technology.In order to cope with these problems,the thesis focuses on the two-pass video compression based on single-pass encoding statistical information.The main research content is divided into the following three aspects.(1)This paper studies the optimization theory of the two-pass video compression algorithm,improves the rate-distortion optimization method,and proposes a rate-distortion optimization algorithm based on the statistical information of the single pass.By analyzing the encoding parameters and encoding residuals of the single pass encoding,the more suitable encoding parameters are set in the two-pass encoding.The Lagrange multiplier is adiusted by establishing the reference value relationship between coding units,which makes the bit allocation of each coding unit is more reasonable to achieve the purpose of the rate-distortion optimization,so the coding quality is improved;(2)This papre studies the rate control model,proposes a rate control algorithm based on statistical information of the single pass.Through the quantization parameters set by the single-pass coding and the number of bits consumed in the coding process,the quantization parameters are modified in the two-pass coding,so that the encoder's rate control algorithm can allocate a more reasonable bits for each encoding unit,so as to improve the accuracy of the code rate control;(3)Based on the theory of probability statistics,this paper establishes a probability distribution model by statistical coding residuals,and proposes a coding optimization algorithm for video motion region.The algorithm obtains the distribution of coding quality through probability statistics and aggregates the worst coding region and the best coding region to the average quality region as much as possible to achieve the goal of smoothing video quality and effectively improving visual quality.The rate-distortion optimization algorithm and rate control algorithm based on the single-pass encoding statistical information proposed in this paper can further improve the video encoding efficiency and control the video transmission quality under the current hybrid encoding framework.The coding optimization algorithm based on the probability distribution model can significantly improve the visual quality of the video.The related work has been adopted into the reference model software by the Chinese Audio and Video Standard(AVS).