Based On Wavelet Domain Video Compression

Recently, many applied image coding algorithms are mixed coding methods based on the spatial motion estimation and compensation, the DCT and quantification of displaced frame difference(DFD) and entropy coding such as some international standards about still images and video compression coding:JPEG,MPEG-1, MPEG-2 and so on. But the algorithms based on DCT have their inherent disadvantage that is "blocking effect". The quality of the restored images is too bad at the high compression ratio. So much more effective coding methods have been gone for. Having the good characteristics of temporal-frequency localization and so on, wavelet transform is very suitable for describing nonstationary signal and adapt to man's vision system. Thereby wavelet transform is increasingly concerned in the field of video compression coding.In this thesis, the author emphatically discusses the theory of the video coding system based on the wavelet field following the basic theory of video coding. Then the multi-resolution motion estimation and image compression coding based on wavelet and are described and analyzed respectively. Make a summary and performance compare of the classical algorithms of image compression. Coding the displaced frame difference (DFD) which is the coefficient difference of the reference frame and the frame formed by multi-resolution motion compensation. The coefficients of DFD are recomposed according to their distributing traits in order to make them coded efficiently and increase the compression ratio. Programming two whole codec system one of which is conventional coding system based on spatial motion estimation and DCT, and the other is based on multi-resolution motion estimation in wavelet field. The shift-variant property of the wavelet transform and three-dimension wavelet transform are also discussed in the thesis. And simulation experiment has been made exploringly for the motion estimation using Low-Band-Shift(LBS) method aim at overcoming the temporal variance of the wavelet transform.The simulation results indicate that the performance of the video codec system based on wavelet field are superior to that based on spatial field not only in coding efficiency but in subjective quality of the decoded image.