| With the rapid development of the Internet IP technology,digital mobile communication technology and multimedia service technology,the users put forward higher requirements on the quality of the video and the visual experience.At the same time,the characteristics of the video itself determines that it has more information than the voice and script,therefore,the coding of video digitization and transmission needs to be compressed.In video coding,the rate control technique is used to control the coding bit rate,so as to adapt to the channel bandwidth.With the advent of a new generation of high efficiency video coding standard protocol H.265/HEVC,The rate control algorithm of H.265/HEVC also arises at the historic moment.H.265/HEVC video coding standard based on R-? model rate control algorithm,the high rate control accuracy,the rate of transmission is more stable.However,in the bit allocation of the image layer,the content characteristics of encoded video can not be fully considered;when the bit allocation of the coding unit layer is not complete,the coding control information is not utilized;As well as the parameter(old olda ?b)update,it can only be updated to the parameters of the current coding unit by updating the parameters of the adjacent coded image / unit;Based on the shortcomings of this algorithm,this paper has done the following res earch:First of all,this paper introduces the background and development history of H.265/HEVC video coding standard,the key technologies in the basic architecture of coding,and puts emphasis on the new key technologies.Introducing the background and principle of rate control,studies the basic theory of rate control algorithm,the basic theory of rate distortion optimization,and the establishment of various rate distortion optimization models.Analysis of the rate control algorithm of symbolic meaning in different stages of the video encoding standard,in-depth analysis of the development process of the rate control algorithm of H.265/HEVC,and the rate distortion optimization model of two kinds of rate control algorithm in H.265/HEVCSecondly,in the analysis of H.265/HEVC based R-? model rate control algorithm,the defect of bit allocation in image layer.In this paper,the corresponding rate control optimization algorithm is proposed,mainly through the performance of the rate distortion optimization theory,optimize the allocation of weights in the image layer bit allocation;at the same time,according to the buffer occupancy rate(filling degree),the bit allocation is dynamically adjusted.The experimental results show that,compared to the HM14.0 rate control algorithm,there are at least 0.88 d B improved for three component PSNR gain,at least 1.09% reduced for coding transmission bit,and at least 1.77% reduced for coding time.Finally,in the research of R-? model rate control algorithm,the accuracy of the bit allocation is not enough and there are some deficiencies in the process of updating parameters.In this paper,the optimization algorithm is proposed,it makes use of the original bits of the current coding unit to carry out the bit allocation of the coding unit layer,and updates the parameters(a?b)by the distortion degree of the coding unit and the characteristics of the video sequence.The experimental results show that,compared to the HM13.0 rate control algorithm,there are at least 0.81 d B improved for three component PSNR gain,at least 0.24% reduced for coding transmission bit,and at least 0.33% reduced for coding time..Compared with the rate control algorithm based on the R-? model,the two kinds of optimization algorithms proposed in this paper have a more prominent effect on the control of the bit rate transmission rate and the bit rate control precision and the rate control coding efficiency. |
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