小波基的构造方法和算法设计

本文首先对小波分析的基本原理作了简要介绍;然后从分解信号完全恢复的角度,对几种典型的小波基进行了概括;并且着重指出:对于两带分解的小波基设计等价于在正则性条件下,设计一个两带完全恢复或近似完全恢复恢复的滤波器组;最后给出了相应于Daubechies基的小波生成算法和实验结果。     

具有紧支撑的正交小波变换滤波器的设计原理和 一种图像精确分解与重构算法

本文通过从一个新的角度研究了Daubechies滤波器的设计原理,得到了具有紧支撑的正交小波变换滤波器设计的两个理论依据,由此构造了一种图像的精确分解与重构算法.该算法非常简单易行,并且与Daubechies滤波器的设计原理是一致的.实验结果表明本文提出的算法能达到无失真的重构.     

基于小波变换的二通道数据采集滤波器组设计

分析了二通道采样系统的基本原理,对其中的信号流程进行了数学推导,研究了基于Daubechies小波的二通道采样系统,对其中小波分解和重构与滤波器组的关系进行了数学分析,用MATLAB仿真验证了采用db4小波对一个超宽带冲激信号进行二通道采样的处理结果。     

用余弦调制PR—FIR方法构造正交小波基

离散小波变换将离散时间信号分解为一系列不同分辨率下的离散近似信号和离散细节．紧支的正交规范小波与完全重构正交镜象滤波器（PR-QMF)相对应。本文在“二带”正交小波基的构造条件下．利用余弦调制完全重构滤波器组的方法．实现了正交小波基的构造，计算模拟表明该方法非常简单、有效。     

基于小波分析的MEMS陀螺信号去噪

介绍了小波基本理论,建立了微机械(MEMS)陀螺的数学模型,将小波变换用于MEMS陀螺信号处理,并且在MEMS陀螺的静态和动态两种情况下,分析比较Daubechies小波的滤波效果,并和二阶IIR滤波器的滤波效果进行比较.仿真结果证明了采用Daubechies小波对MEMS陀螺信号去噪的有效性和可行性.     

一种选择多小波预滤波器的方法

提出了多小波(Multiwavelet)预滤波器的选择原则—预滤波和多小波变换对原数据不引入任何形式的信息损失或失真,该原则对应于预滤波器和多小波滤波器组在频域内能谱密度恒为常数．在此基础上,得到了常用多小波预滤波器应满足的必要条件．提出了用于数据压缩的预滤波器的选择方法,该方法以数据高低频成分分离的分离效率为选择准则．以此准则,给出了常用多小波的最佳预滤波器．仿真实例证实了这种方法的有效性．     

改进的DWT-MFCC特征提取算法

基于离散小波变换的美尔倒谱系数(DWT-MFCC)~([1])将小波变换引入到MFCC参数的提取中,用DWT代替FFT将语音信号分解为多个频带的小波系数,并将小波系数的频率响应直接拼接为完整频谱后再通过Mel滤波器获得。改进的DWT-MFCC特征提取算法从滤波的角度分析小波分解过程及各子带频谱的变化,提出了新的有效频谱拼接方式。实验结果表明,改进的特征提取算法提高了说话人的识别率;同时,在该算法下随着小波滤波器db N长度的增加,滤波器截止特性变好,识别率也随着增加。     

一种小波分解滤波器高速实现结构

近年来,小波变换得到了广泛的应用,快速塔式分解算法是它应用的一个有利工具,其地位相当于FFT之于Fourier分析,因此DWT的快速硬件实现变成了其应用的一个重要问题,本文通过将并行systolic FIR滤波器结构引入小波分解滤波器的设计,得到了一种小波分解滤波器的实现结构。该结构由于应用了systolic技术及采用并行结构,除了可以提高运算速度外,还可以提高系统的数据吞吐率以及降低系统功耗。     

基于双正交小波的光阑小波滤波器

提出了一种应用于4f光学系统的光学小波滤波器的设计与制作方法.结合光学信号的优势与小波变换的优点,利用双正交小波的共轭镜像特性构造出了频域形式的分解和重构滤波器.通过将滤波器放置在4f系统的频谱面上对图像成功实现了二维分解和重构.另外还根据信息处理要求和采样器件的特性,制作了振幅型和位相型两种小波滤波器.这两套滤波器都...     

光纤通信中小波去噪预处理技术研究

为了降低随机噪声对信号处理时带来的负面影响,增强信号的有用部分,研究基于Daubechies小波滤波的信号预处理算法。随着小波分解层次的增加,去噪效果能够得到改善,实现了信号的有用部分与噪声的有效分离。     

纯二维全相位滤波器组及其在图像压缩中的应用

基于全相位理论,设计了3种纯二维全相位滤波器组(ADFB).这些滤波器组可以直接对图像进行纯二维分解和重构,若忽略滤波器的有限精度问题,系统是全重建的.为了减小运算量,纯二维ADFB采用提升格式实现.仿真试验表明,纯二维ADFB具有良好的数据压缩特性.在压缩率相同的情况下,尤其是IDCT-AFB7.7比Daubechies9/7小波重建图像的峰值信噪比(PSNR)最多小0.7 dB,这与采用的适合于可分离二维小波变换的四叉树SPIHT编码方案有关,若采用二叉树SPIHT编码,会使压缩效果得到改善.     

Optimization of wavelet decomposition for image compression and feature preservation

A neural-network-based framework has been developed to search for an optimal wavelet kernel that can be used for a specific image processing task. In this paper, a linear convolution neural network was employed to seek a wavelet that minimizes errors and maximizes compression efficiency for an image or a defined image pattern such as microcalcifications in mammograms and bone in computed tomography (CT) head images. We have used this method to evaluate the performance of tap-4 wavelets on mammograms, CTs, magnetic resonance images, and Lena images. We found that the Daubechies wavelet or those wavelets with similar filtering characteristics can produce the highest compression efficiency with the smallest mean-square-error for many image patterns including general image textures as well as microcalcifications in digital mammograms. However, the Haar wavelet produces the best results on sharp edges and low-noise smooth areas. We also found that a special wavelet whose low-pass filter coefficients are 0.32252136, 0.85258927, 1.38458542, and -0.14548269) produces the best preservation outcomes in all tested microcalcification features including the peak signal-to-noise ratio, the contrast and the figure of merit in the wavelet lossy compression scheme. Having analyzed the spectrum of the wavelet filters, we can find the compression outcomes and feature preservation characteristics as a function of wavelets. This newly developed optimization approach can be generalized to other image analysis applications where a wavelet decomposition is employed.     

Three-dimensional video compression using subband/wavelet transformwith lower buffering requirements

Three-dimensional (3-D) video compression using wavelets decomposition along the temporal axis dictates that a number of video frames must be buffered to allow for the temporal decomposition. Buffering of frames allows for the temporal correlation to be made use of, and the larger the buffer the more effective the decomposition. One problem inherent in such a set up in interactive applications such as video conferencing, is that buffering translates into a corresponding time delay. We show that 3-D coding of such image sequences can be achieved in the true sense of temporal direction decomposition but with much less buffering requirements. For a practical coder, this can be achieved by introducing an approximation to the way the transform coefficients are encoded. Applying wavelet decomposition using some types of filters may introduce edge errors, which become more prominent in short signal segments. We also present a solution to this problem for the Daubechies (1988) family of filters.     

探地雷达回波信号小波压缩方法研究

介绍了多分辨分析和小波变换的基本理论以及常用小波变换压缩数据的三种方法：只保留近似信号；全部保留近似信号及细节信号中的较大值；保留近似信号及细节信号中的较大值。将紧支集小波（Daubechies)和正交三次B-样条小波压缩探地雷达数据进行了对比，计算表明正交三次B-样条小波变换方法效果较好，而在全部保留近似信号及只保留细节信号中数值较大的系数时，压缩比大而重建雷达数据与原始雷达数据间的均方差较小。     

New filter banks and more regular wavelets

One of the most interesting features of a wavelet is its Sobolev regularity. In this paper, we construct new wavelets that are more regular than the Daubechies wavelets for a given support width. We tabulate the coefficients of the new filters to make them easily accessible. We show that these filters outperform the Daubechies filters in the L² approximation of the ideal filter. An application for speech analysis, synthesis, and compression is provided     

一般的9-7小波滤波器及其图像压缩性能研究

通过构造一个包含Cohen和Daubechies等人的著名9-7小波滤波器(CDF97)的超小波滤波器族,获得了新的9-7小波滤波器,它们不仅有很好的压缩性能,也有很好的计算性能,有利于ASIC的设计.试验结果表明,新的小波滤波器几乎具有CDF97的客观压缩性能,并且能保留更多的图像细节.因此,在标准化图像压缩系统中,本文的滤波器是CDF97理想的替代者.