Researches On The Video Coding Related Techniques Based On Visual Optimization

With the development of information technologies, video applications have gainedincreasing popularity in modern life. But in view of the huge size of video data, videocoding is often necessary in practice for compression purposes. And researches andapplications on video coding related techniques are also promoted correspondingly.Since human eyes often act as the ultimate receivers of video, it’s often desiredto take into account the visual characteristics in video coding related techniques. Nowalthough there have been many research achievements for video coding related tech-niques considering visual characteristics, with the introduction of new video codingstandards and transmission protection methods, corresponding video coding relatedtechniques based on visual characteristics still deserve further researches. And thisthesis just puts its emphasis on the researches on the video coding related techniquesbased on visual optimization.Researches on video coding related techniques focus mainly on encoding, trans-mission and decoding. And this thesis also selects the research topics from these threeaspects.Usually visual characteristics are taken into account at the encoding stage byperceptual coding. In this thesis, firstly a method of perceptual coding based on theH.264/AVC standard is proposed. First, the distribution of visual sensitivity is estimat-ed through a Just Noticeable Distortion (JND) model in the classic DCT domain. Thenthe corresponding JND thresholds are translated to those of the H.264/AVC transformdomain, which are used to suppress the transform coefficients of prediction residualsadaptively. Besides, the Lagrange multiplier for rate distortion optimization is alsoadapted to coding with coefficient suppression in terms of equivalent distortion. Theproposed method is fully compatible with the H.264/AVC standard. Experimental results show that at similar visual quality, the method can obtain obvious bit savingcompared with the JM14.2reference software when the quantization parameter (QP)is less than28, and can obtain more bit saving than Chen’s method in most cases.As common channels usually suffer from transmission errors inevitably, suitableerror resilient methods are often necessary during video transmission. In this thesis,secondly in view of the recently developed fountain channel codes—Raptor codes,Unequal Error Protection (UEP) methods based on Raptor codes are explored. Dif-ferent from many existing methods, standard Raptor codes are adopted here for betterpracticality. By making use of the good characteristics of Raptor codes at large blocklength and the priorities of video packets, we propose respectively a baseline and anenhanced UEP method, which have different complexities. Besides, we also give anefficient algorithm to optimize the configuration of the proposed methods. Experimen-tal results show that both the objective and the subjective quality of video can be betterimproved by our methods than the GRIP method in case of packet losses.Error concealment is often utilized at the decoding stage to improve the visualquality. In this thesis, thirdly according to the property that human eyes usually paymore attention to region of interest (ROI) in images, an improved error concealmentmethod of ROI based on the H.264/AVC standard is proposed. At the encoder side,the motion vector information of ROI macroblocks is embedded in the backgroundbased on original quantized coefficients of background macroblocks. Considering thelimited embedding capacity of the background, we further propose to determine theembedding priorities of ROI macroblocks based on a predefined metric of error prop-agation. The method is fully compatible with the H.264/AVC standard, and can be ap-plied jointly with many other error concealment methods. Experimental results showthat the method can improve the error concealment of ROI better than the DMVEalgorithm and the improved BMA algorithm without much loss of coding efficiency.