Researches On Rate Control Algorithms For HEVC Based On Scene Change

With the development of the multimedia communication technology,the rapid growth of the size of data in HD and UHD video,brings a big challenge to the network translation and data storage.The next generation video coding standard(HEVC)provides a powerful ability of video compression.However,with the limits of both network bandwidth and storage capacity.There is still a research problem that how to ensure a high quality of the video image in the field of video compression.The rate control technology played a very good role in this respect.The current HEVC rate control has achieved a good R-D(RateDistortion)performance and a high accuracy of output bitrate.As we all known,scene change is common phenomenon in the actual video sequence that will influence the performance of the rate control if ignore it.But the current HEVC rate control ignore the scene change in the actual video sequence,it is easy to cause a unreasonable bit allocation and then result in quality degradation in video coding frame.To overcome the problem,the main researches of this paper for HEVC rate control are listed as follows:First of all,this paper have studied the theoretical research of rate control technology deeply,including the key technology of HEVC standard is describing brief ly,the research status and the basic principle and the process of rate control technology are illustrated in detail.What’s more,the three typical models of rate control and the latest HEVC rate control algorithms are analyzed and compared.At the same time,the disadvantages of the current HEVC rate control algorithms in the background of scene change are expound,and the complexity of the scene which is an important factor that affects the bit allocation is pointed out.So the research of this paper for HEVC rate control under scene change is elicited.Secondly,Through theoretical derivation and analysis,the current HEVC rate control employ an average bit allocation in GOP(Group of Picture),in the background of scene change,which will result in the bit allocation unreasonably and the quality degradation in coding frame.To solves the problem,this paper present a rate control algorithm for HEVC based on scene change: First,the complexity of scene is measured by the average difference of component of Y between two consecutive frames,and then is applied to bit allocation in GOP level.What’s more,when a scene change was detected,some parameters such as model parameters,the current GOP and the current frame,will be adjusted to improve the quality of coding frame.In this process,the scene change detection algorithms will be also improved to detect accurately.Finally,The proposed algorithm and other improved algorithms are simulated and implemented under HM16.5 platform.On the basis of a lot of experiments,the performance between proposed algorithm and other algorithms will be compared and analysis with authoritative evaluation indexes.The comparison and analysis results show that compare with the rate control in HM16.5,the proposed algorithm can reduce 12.91% encoding time,and improve the average PSNR-Y of sequence 0.77 d B,and maintain the bitrate error under 0.1%.So,in the background of scene change,the proposed algorithm can efficiently reduce the negative influence of scene change.Compared with algorithm in HM16.5,the encoding efficiency and image quality are both had a certain improvement,and the output bitrate is also maintained accurately.The applicability of this algorithm will be more obviously especially in the case of uneven distribution of the scene.