Research On Rate Control Techniques For HEVC

Video compressing brings various conveniences to our daily life,work and entertainment,such as high resolution video,videophone,video conference,and so on.Video coding technology,which is video compressing based on,has achieved considerable development in the past decades.From the earlier H.261 to current HEVC,video coding technology has established the hybrid coding framework through many generations' evolution.In all of those coding technologies,rate control always plays a key role.In real video application,due to the limitation of band width,how to keep the coding quality under limit bitrate,and realize output stream bitrate stability,which is called rate control problem.Except for accurate rate control,how to solve the problems that video coding quality usually has a low performance under rate control mode,and rate control gives a poor support to parallel coding framework,which have become the research focuses.About how to improve the coding quality under rate control mode,this paper proposed a temporal dependent bit allocation scheme for HEVC rate control.In traditional rate control algorithm,bits are allocated to different unit according to their context complexity.In our temporal dependent bit allocation scheme,the temporal correlation is also adopted in.Specifically,if someone unit is referenced many times in the future frames,which means it has a higher temporal weight,we should consider allocating more bits to it in order to improve its coding quality.This way can ensure that all the temporal related units' coding quality.This paper describes the algorithm procedure and implementation issues of this temporal dependent bit allocation scheme in detail.Experiments validate the effectiveness and analyze the coding complexity.About how to improve the support to parallel coding under rate control mode,this paper proposed a joint rate control scheme for multi-machine parallel coding framework.Through independent frame bit allocation and adaptive slice bit allocation,this scheme can achieve enough rate control accuracy under parallel coding.As we know,the fashion of parallel coding framework brings the challenge of data dependency,and higher parallel degree will lead to higher data correlation unavailable.This brings a huge bad influence to accurate rate control,because rate control exactly bases on the temporal and spatial correlation of video data,which makes it possible that dynamically adjusting the coding parameter according to history coding information to achieve global rate stabilization.The joint rate control scheme proposed in this paper through periodically collecting independent coders' information and reset appropriate coding parameter after synthesize all coders' real-time coding state.Experiments validate that this scheme can effectively keep output rate under stable target bitrate.