基于小波域的视频压缩编码

【作者】 尚艳霞；

【导师】 李建华；

【作者基本信息】 大连理工大学 ， 信号与信息处理， 2003， 硕士

【摘要】 目前，许多实用的图像编码算法都是基于空间域的运动估计和补偿、预测误差的DCT及量化以及变换系数的熵编码的混合编码方法，如有关静止图像和视频图像的国际标准JPEG，MPEG-1，MPEG-2等。但基于DCT的算法有其固有的缺点，即方块效应，在压缩比较高时，图像质量会很差，因此人们一直在努力研究寻找更为有效的编码方法。小波变换具有良好的空间一频率局域化等特性，非常适合描述非平稳图像信号，适应人的视觉系统特性，从而在视频编码领域受到越来越多的关注。 本文在介绍了视频编码基本原理的基础上，重点研究了基于小波域的视频编码系统的工作原理，分析了小波域的多分辨率运动估计和小波域的图像编码方法，总结了小波图像编码的经典算法，并对它们进行了性能比较，分析了多分辨率运动补偿后预测误差系数的分布特点，对量化后的预测误差系数的组合进行了改进，使之能更有效地编码，从而提高编码效率。编程实现了两个完整的编解码系统：传统的基于空间域运动估计、DCT变换的视频编码和基于小波域多分辨率运动估计的视频编码。论文还对利用三维小波变换进行视频编码以及小波变换存在的移变性进行了分析讨论，并介绍了克服这种移变性的低子带位移运动估计的方法，探索性地进行了计算机仿真。 计算机仿真结果表明，基于小波域的视频图像编解码系统无论从编码效率，还是从解码后的图像主观质量比基于空间域的编解码系统都有了一定程度的提高。更多还原

【Abstract】 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.更多还原