Frame-skipping Transcoding And Its Security Policy Research Based On H.264/AVC

Based on the calculation of cost value for Rate-distortion Optimization (RDO),H.264/AVC searches all coding modes given criteria for rate distortion value in turn, then,takes the mode with the minimum value as the optimal coding mode. Frame-skippingtranscoding focuses on solving compatibility problems of video streaming among differentnetwork environments, it will reduces the transcoding efficiency if just use the same RDOtechnology simply. This paper focuses on Frame-skipping transcoding technology based onH.264protocol, centre on the study of quick decisions for coding mode and security policyissues in video transcoding. Full search mode selection method of H.264is cumbersome andtime-consuming, significantly, it will restrict, reduce the efficiency of frame-skippingtranscoding. This paper presents a fast mode selection strategy with the improvedperformance for frame-skipping transcoding, which not only improves coding efficiency butalso ensures the better video quality. Study in detail is as follows:(1) With the analysis of the information contained in the input video stream offrame-skipping transcoding, as well as two motor thresholds, the improved mode selectionstrategy uses a core function that can be more approximate to get the real movement ofcurrent macroblock, which enable the algorithm to depict and determine the motioncharacteristics of current macroblock more accurately. The fast mode selection strategy solvesthe mapping using of mode information reasonably under frame-skipping transcodingconditions, which ensure that, after transcoding, the algorithm obtains more reliable videoquality, which can be widely applied to real-time interactive video under a variety andcomplicated network.(2) In order to avoid the reference of inter-coded macroblock to trigger error diffusion, inthe intra-coding, H.264use above and left neighboring pixels which have been coded toexecute predictive coding. This paper adopts simple mapping strategy for intra predictionmode decision in frame-skipping transcoding to reset intra-prediction mode, which acceleratetranscoding efficiency further.(3) Aim at the polytropic change motion problem of video sequence, introduce a set ofadaptive threshold for inter mode selection, which can change the threshold value of motioncharacteristics flexibly according to the different motion movement of macroblock in order to achieve adaptivity. Therefore, the algorithm ensures the motion characteristics of macroblockwaiting to encode to be judged more accurate, which will get more guaranteed video quality.Combined the mode information of frame that is discarded and can never be recovered intranscoding, present a simple effective encryption policy, which avoid the disadvantages ofthe increasing of itself capacity triggered by the traditional encryption algorithm.Innovative research this subject uses JM platform that is H.264reference model toexecute the simulation experiment, and the experiment adopts different video sequencescontaining fast, medium and slow motion feature videos to verify the improved algorithmproposed in this paper. Under the conditions of guaranteed and high transcoding efficiency,the improved algorithm gains the expected reliable video quality. Furthermore, encryptionpolicies of video security proposed here achieve the desired effect and efficiency ofencryption, which broaden the prospect of video security technology.