| The hybrid video coding technique(motion compensation prediction technique and coding technique based on DCT)is applied in the international Video Compression Coding Standard of H.264/AVC and H.265/HEVC;in hybrid video coding technique,the core algorithm of encoder is inter-frame prediction.The inter-frame prediction can be used to wipe out the redundant information of time domain in video sequence,which includes integer pixel motion estimation and fractional pixel motion estimation.In motion estimation,the correlation between pixels can be used to complete the interpolation of fractional pixel value to improve the veracity of motion vector estimation so that smaller residual data can be generated in motion compensation process.Experimental results show that the high-precision motion compensation can enhance the compression efficiency of video coding as well as the motion estimation performance,and meanwhile lead to heavy computation and frequent memory operation.The order of filter can determine the read-in amount of reference data and how to reduce the complexity of interpolation on the premise that the prediction accuracy is guaranteed has become a major problem.In this thesis,depending on the “Study on High Efficient Video Coding Based on Flexible Quad-tree Mode and Improved DCT”of National Natural Science Foundation of China and the “Study of Filtering Algorithm and DCT Optimization Facing HEVC” of Science and Technology Research Project of the 13 th Five Year of Jilin Provincial Education Office,the research status for the theories and techniques of video compression encoding,the development process of international video coding standard and the methods and principles for video image interpolation are analyzed and the sub-pixel motion compensation technique as well as the VLSI structure design are studied profoundly to lay the foundation for the further constructing more efficient H.265/HEVC video coding.The sub-pixel motion compensation technique can increase encoding and decoding computation and memory access complexity while improving video coding performance.In this thesis,the algorithm for sub-pixel interpolation filtering optimization of H.264/AVC and H.265/HEVC standard,the high efficient interpolation filtering of HEVC motion compensation and Adaptive Interpolation Filter and VLSI structure design are lucubrated and the following results are obtained:(1)Improved H.264 sub-pixel interpolation filtering algorithm In order to improve the efficiency of video coding of H.264/AVC standard,the improved H.264 sub-pixel interpolation filtering algorithm is put forward,namely sub-pixel interpolation algorithm whose filter coefficient is variable and coefficient sum is invariable and the sixth order filter is replaced by fourth order filter.In this algorithm,cubic convolution is applied to acquire the coefficient of interpolation filter,directional interpolation filter is used to obtain the sample of sub-pixel position and optimization is done while encoding GOP structure.The experimental results show that in terms of complexity,compared with H.264 standard algorithm,the algorithm in this thesis reduces the space complexity by 19% and decreases the visitor volume,but increases the computation complexity.In terms of coding performance,compared with H.264 standard algorithm,the algorithm in this thesis enhances PSNR value by 0.38 d B and reduces bit rate by 4.74% averagely.Hence,the algorithm posed in this thesis can improve video sequence coding performance of different movement degree.(2)Sub-pixel interpolation algorithm based on adaptive filterSince the coding performance can not be further improved if the filter of same order is used to interpolate for the video sequences of different resolutions,the sub-pixel interpolation algorithm based on adaptive filter is put forward.In the algorithm,the interpolation filters of different orders(namely,resolution ratio R?2560×1600,select fourth order filter;1280×720?R<2560×1600,select sixth order filter;R < 1280×720,select eighth order filter.)can be selected automatically according to 3 given video sequences;within the video sequence area of 3 different resolution ratios,the high order interpolation filter can be replace by low order interpolation filter according to the correlation between pixels to realize the adaptive selection of filter.Conduct sub-pixel motion compensation interpolations in 3 video sequence areas with different resolutions and use original images to replace half pixel pictures and the acquired half pixel pictures to replace quarter-pixel pictures so as to realize AF_FIA algorithm optimization.The experiment results show that compared with filter of HEVC standard,the fourth order filter can reduce 32% and sixth order filter can reduce 16% of space complexity.In terms of computation complexity,both fourth and sixth order filters reduce sharply the multiplication and addition compared with HEVC;in particular,the amount of multiplication and addition is less than 1/3 of HEVC;the space complexity of eighth order filter is same to HEVC,and the computation complexity is improved to some extent with small influence on video coding of low resolution.In terms of coding performance,both the algorithm by IBBP and IPPP coding structures has improved the peak noise rate and coding performance with good robustness and reduced bit rate compared with HEVC standard algorithm.(3)Adaptive Interpolation Filter Algorithm Based on HEVCIn order to further improve video quality of adaptive sub-pixel interpolation algorithm and reduce computation complexity,adaptive interpolation filter algorithm based on HEVC is put forward.This algorithm encodes within the video coding framework of new coding standard H.265/HEVC to raise efficiency of video coding;through the symmetric optimization of filter coefficients,the filter coefficients demanded by code stream and the complexity of decoding computation are reduced.The experimental results show that in terms of complexity,compared with NS_AIF algorithm and S_AIF algorithm,the interpolation filter coefficient demanded by AIF_HEVC algorithm is reduced sharply,equivalent to filter coefficient of MD_AIF algorithm,but higher than D_AIF algorithm.Compared with S_AIF algorithm,D_AIF algorithm and MD_AIF algorithm,the computation complexity of AIF_HEVC algorithm is reduced greatly.In terms of coding performance,compared with D_AIF algorithm,S_AIF algorithm,CMD_AIF algorithm and AF_FIA optimization algorithm,the coding performance of AIF_HEVC algorithm is improved with good robustness no matter IBBP encoding structure or IPPP encoding structure is applied.(4)VLSI structure design of high efficient interpolation filtering for HEVCSince the high data throughput and memory access amount are the bottleneck problems for the decoder of HEVC standard,a VLSI structure design of high efficient sub-pixel interpolation filtering facing HEVC is put forward.Firstly,the reusable eighth order filter structure is designed based on the inversion symmetry of filter coefficient;secondly,the parallel design and sub-pixel interpolation calculation scheme of pipeline architecture are put forward;finally,the two parallel 8 input interpolator are posed based on the traditional single input channel interpolator.The test results show that the interpolation structure in terms of processing time and throughput are superior to other design methods,and can achieve the same HD/Ultra HD video real-time transmission at a lower operating frequency,thereby reducing the transmission power consumption.The proposed 8-input dual-channel interpolation filter structure can be completed at a frequency of 34.2MHz at 1920×1080 @ 30 fps video decoding needs.At the same time,to meet the 3840×2160 @60fps real-time video transmission. |
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