Study On Rate Control Algorithm For H.264Video Coding

Only the syntax structure regulation of bitstream for video compression standard wasstipulate while the rate control algorithm is open for most occasion.It is should designdifferent rate control algorithm for different applications.The performance of rate controlalgorithm directly affect the quality of video, therefore it is an important significance toprovide an rate control algorithm which performance well for video coding.Rate control algorithm is one of the most important parts of video coding.The target ofrate control algorithm is provide an practical application between the the video quality andactual bitrate.For a rate control algorithm which performance well,it is should not only obtainexcellent video quality but also to guarantee the stability of bitstream for transmissionsuitable.Rate control is developed on the basis of rate distortion.Because of the adoption ofrate-distortion for mode selection,the rate control algorithm become more difficult torealize.A reasonable rate control algorithm may get a reasonable balance between codequality,buffer control,rate control and the number of frames jumped.This paper introduced some key technologies for new generation video compressionstandard for H.264/AVC first,such as inter/intra prediction、entropy coding、discrete cosineintegral transform and so on.Then introduced the rate control algorithm for H.264/AVC、therelation between rate control algorithm and rate distortion、the classical rate control proposalof JVT-G012and so on.The main content as follows:(1) The video sequence is generally not made up of a single scene,but contain differentscenarios.When scene switching appear in the video sequence, the correlation between framesgreatly decrease, therefore the traditional rate control strategy may lost its efficacy to dealwith scene switching.As a result,in order to solve this problem,a method to process sceneswitch is put forward in this paper.First,detection scene switching with average greyvalue,and then proposes two GOP(GOP of Pictures)restructuring methods but also the rateupdate method and the quantitative parameter calculation.The experimental resultsdemonstrate that the new scheme can obtain a more accurate bitrates while the quality ofvideo improved on average.(2) The average quantitative parameter of previous GOP is used as the QP for I-slicecoding of current GOP for the rate control proposal of H.264/AVC.To a certain extent,thismethod is lack of accuracy.Therefore,for the inaccurate calculation of quantitative parameterfor I-slice which may cause the inaccurate buffer control and the poor video quality,a methodfor I-slice quantitative parameter calculation which is more suitable for practical application is proposed.In this paper,the QP of I-slice of current GOP is rely on the buffer occupancy whenprevious GOP encoded and the rate of frames skiped and the current buffer occupancy.Theexperimental results show that the new method is performance well for bitrates,the actualbitrate is more closer to the target bitrate, and with a higher PSNR at the same time, thenumber of frames skipped is decline,the PSNR curve fluctuations smaller.