Research On Inter Prediction?Rate Control And Rate-distortion Optimization Techniques In Video Coding

With the rapid development of emerging technologies,science and technology are all keep up with the times.Also video applications are becoming more diversified and ultra-clear,which has promoted the development of the next-generation video coding standard H.266.Compared with the previous generation video coding standard H.265,the latest coding standard improves coding efficiency by 30% under the same video sequence and test conditions.The video coding standards have adopted a hybrid video coding framework,and the H.266 coding standard has also adopted the same framework,and related technologies of coding standard have been improved,such as block division,intra prediction,inter prediction amd so on.The thesis studies and analyzes techniques related to inter prediction,bit rate control,and rate distortion optimization in video coding,optimizes and improves the key technologies of them,and achieves corresponding coding gain.The related research work and innovations are shown in the following three aspects:1.Motion vector information is very important in inter prediction.Finer motion vector accuracy can lead to more accurate predictions,resulting in less estimated distortion,finally remove temporal redundancy between frames effectively.In the latest coding standard H.266/VVC,there are three types of motion vector resolution,and a variable-length flag that needs two bits to encode are used to transmit motion vector information.The thesis mainly focuses on the frame-to-frame correlation information,and calculates the related motion vector resolution information in the previous frame.The motion vector resolution information in the frame to be encoded refers to the information in the previous frame,and uses the highest amount of motion vector resolution information which will be allocated the fewest bits for transmission,and conversely,uses the lowest amount of motion vector resolution information which will be allocated the most bits,so as to achieve the adaptive allocation of the bits occupied by the flag which transmit motion vector resolution information,to save coding bits and improve coding efficiency.2.Aiming at the temporal dependent rate distortion optimization problem in the random access configuration hierarchical coding structure of the new coding standard H.266,the thesis focuses attentions on analyzing the hierarchical temporal dependency on condition that the size of group of picture is equal to 16,and establishes a temporal propagation chain,finally estimates the distortion to obtain the Lagrange multiplier,which solves the problem of rate distortion optimization.During the estimation of distortion,the thesis brings in the weight distortion factor to modify the distortion,which make the distortion estimation more accurate.Secondly,the hierarchical QP was adjusted,which will affect aggregation factor.At last,the Lagrangian multiplier was modified according to the aggregation factor.The method has a good coding effect on the general test sequences.Among them,the coding effect of sequences with similar background is significant.3.Bit rate control includes target bit allocation and determination of quantization parameters two steps.Target bit allocation is divided into GOP level,frame level,and CTU level.When the size of group of picture is equal to 16,the thesis proposed a new frame-level target bit allocation based on the lambda domain.The frame-level target bit allocation is divided into uniform bit allocation,fixed bit allocation and adaptive bit allocation.In the fixed bit allocation,the bits used in each layer of the pictures in the general test sequences are counted,and the bit weight is assigned to each layer of the pictures according to the least square method.In the adaptive bit allocation,counting the lambda value which exsist in each layer of the first GOP of the general test sequence QP from 19 to 35,further obtain the weight of each layer of lambda,finally the quantization parameter is finally determined.The algorithm play a good bit rate control effect on the H.265/HEVC coding standard reference software HM16.15 and achieves a favourable coding gain.