Dissertation > Industrial Technology > Radio electronics, telecommunications technology > Communicate > Image communication, multimedia communication > Image coding

Research and Implementation of Dwt-based Video Codec System at Low Bit Rates

Author XuLinBo
Tutor XuYongBing
School Huazhong University of Science and Technology
Course Computer technology
Keywords Discrete Wavelet Transform Significant test Backward prediction Refinement of mathematical morphology
CLC TN919.81
Type Master's thesis
Year 2011
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In the video or image coding , discrete wavelet transform (DWT) , compared to the discrete cosine transform (DCT) with scalability, no blocking effect , and are consistent with the advantage of the human visual system . To this end , the latest video coding standard H.264 modeled , the analysis of its principle , structure and key technologies , elaborates JPEG2000 is how to use wavelet transform coding , and as a basis for a low DWT-based video codec bit rate . By a first-order two - dimensional discrete wavelet decomposition, the separated high and low frequency components of each frame of the video series are processed separately. The low frequency part of the H.264 coding compression; high frequency portion is divided into the I - and P-frames are encoded , based on the characteristics of the wavelet coefficients , P frames with backward prediction techniques to predict , and using mathematical morphology Refinement method correction , cyclical the transmission of I frame data after the passage to the inter - frame motion vector prediction and motion compensation , the high - frequency part of the P frame to strengthen and reduce the P frame error accumulation ; the other hand , the I frame only encoding the significant coefficient of transmission in a specific proportion superset of significant coefficients, and using the adaptive scan mode , the run-length coding and variable length coding of these ultra significant coefficient encoding compression . In addition , in-depth research and analysis of the key modules in the system to achieve specific performance . Optimization of the wavelet basis selected , high-frequency significant coefficient backward forecasting , mathematical morphology thinning algorithm , entropy encoding , and the entire system of coding control and other issues specific analysis and simulation . Experimental results show that at low bit rates , the overall performance of the video coding scheme is better than H.264 , especially I - frame encoding , and its performance is significantly better . Strong texture detail and the quality of the reconstructed video retention capacity , the outline of the image is clearer , subjective visual quality has a larger increase .

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