一种基于二进制小波变换的无损图像编码算法

该文提出了一种基于二进制小波变换的嵌入式无损图像编码算法渐进式分裂二进制小波树编码器(PPBWC)。PPBWC采用混合系数扫描方法按模值大小排序小波系数得到中间符号序列,通过非因果的自适应上下文条件编码考虑了不同频带小波系数的自相似特性,并利用待编码系数的未来信息提高了PPBWC的压缩编码性能。混合系数扫描和非因果的自适应上下文条件编码是PPBWC高效编码的主要因素。实验结果表明,与其它嵌入式无损算法相比,PPBWC具有最优的无损编码性能。     

图像的无损压缩编码方法及JPEG标准模式

概述了经典图像编码方法和无损数据压缩编码方法，分析了其基本思想和性能，介绍了图像压缩编码的国际标准。并指出图像压缩编码正处于蓬勃发展之中。     

A New Semiparametric Finite Mixture Model-Based Adaptive Arithmetic Coding for Lossless Image Compression

In this paper, we propose a new approach for block-based lossless image compression by defining a new semiparametric finite mixture model-based adaptive arithmetic coding. Conventional adaptive arithmetic encoders start encoding a sequence of symbols with a uniform distribution, and they update the frequency of each symbol by incrementing its count after it has been encoded. When encoding an image row by row or block by block, conventional adaptive arithmetic encoders provide the same compression results. In addition, images are normally non-stationary signals, which means that different areas in an image have different probability distributions, so conventional adaptive arithmetic encoders which provide probabilities for the whole image are not very efficient. In the proposed compression scheme, an image is divided into non-overlapping blocks of pixels, which are separately encoded with an appropriate statistical model. Hence, instead of starting to encode each block with a uniform distribution, we propose to start with a probability distribution which is modeled by a semiparametric mixture obtained from the distributions of its neighboring blocks. The semiparametric model parameters are estimated through maximum likelihood using the expectation–maximization algorithm in order to maximize the arithmetic coding efficiency. The results of comparative experiments show that we provide significant improvements over conventional adaptive arithmetic encoders and the state-of-the-art lossless image compression standards.     

A Lossless Compression Method for Medical Image Sequences Using JPEG-LS and Interframe Coding

Hospitals and medical centers produce an enormous amount of digital medical images every day, especially in the form of image sequences, which requires considerable storage space. One solution could be the application of lossless compression. Among available methods, JPEG-LS has excellent coding performance. However, it only compresses a single picture with intracoding and does not utilize the interframe correlation among pictures. Therefore, this paper proposes a method that combines the JPEG-LS and an interframe coding with motion vectors to enhance the compression performance of using JPEG-LS alone. Since the interframe correlation between two adjacent images in a medical image sequence is usually not as high as that in a general video image sequence, the interframe coding is activated only when the interframe correlation is high enough. With six capsule endoscope image sequences under test, the proposed method achieves average compression gains of 13.3% and 26.3 % over the methods of using JPEG-LS and JPEG2000 alone, respectively. Similarly, for an MRI image sequence, coding gains of 77.5% and 86.5% are correspondingly obtained.     

基于整数小波变换的有损与无损嵌入式图像压缩

提出了基于整数小波变换的嵌入式图像编码方案，能够进行有损和无损两种模式的图像压缩，在非常低的比特率时能够获得较高质量的重构图像。该方法适合图像的渐进传输，它是使用扩增的零树信号和位面编码的合成技术，最后对产生的符号流进行算术编码。文中给出了该方法与有损和无损压缩标准的性能比较。     

用整数小波结合改进SPIHT编码实现静止图像无损压缩

无损图像压缩是图像处理中的一个重要领域 ,传统的基于熵编码的无损压缩编码方式存在一定的局限。利用提升算法构造整数小波变换 ,然后针对无损压缩特点 ,对 SPIHT算法加以改进 ,实现了一种可行的图像无损压缩编码方案。实验表明 ,优于传统熵编码和直接采用 SPIHT的无损压缩方法     

图像灰度级动态分段的无损压缩编码方法

文中提出了一种新的无损图像压缩编码方法．通过对图像灰度值按四种情况进行动态分段编码压缩,对于不同的图像会有不同的分段选择,因而具有一定的自适应性．实验证明,这种压缩方法具有很好的压缩效果．     

Linear-Codes-Based Lossless Joint Source-Channel Coding for Multiple-Access Channels

A general lossless joint source-channel coding (JSCC) scheme based on linear codes and random interleavers for multiple-access channels (MACs) is presented and then analyzed in this paper. By the information-spectrum approach and the code-spectrum approach, it is shown that a linear code with a good joint spectrum can be used to establish limit-approaching lossless JSCC schemes for correlated general sources and general MACs, where the joint spectrum is a generalization of the input–output weight distribution. Some properties of linear codes with good joint spectra are investigated. A formula on the “distance” property of linear codes with good joint spectra is derived, based on which, it is further proved that, the rate of any systematic codes with good joint spectra cannot be larger than the reciprocal of the corresponding alphabet cardinality, and any sparse generator matrices cannot yield linear codes with good joint spectra. The problem of designing arbitrary rate coding schemes is also discussed. A novel idea called “generalized puncturing” is proposed, which makes it possible that one good low-rate linear code is enough for the design of coding schemes with multiple rates. Finally, various coding problems of MACs are reviewed in a unified framework established by the code-spectrum approach, under which, criteria and candidates of good linear codes in terms of spectrum requirements for such problems are clearly presented.      

可提高编码效率的MPEG-4音频可伸缩无损编码

最近提出的MPEG无损音频编码标准(MPEG-4音频SLS(scalable to Lossless编码技术)提供了一种统一的语音模式,这种语音模式可以将有损语音编码,无损语音编码以及粒度可伸缩语音编码的功能结合在 一个框架中.我们提出了两种提高SLS编码效率的方法,即基于上下关系的算术编码方法和低能量模式编码方法.这两种方法同当前的SLS框架搭配在一起运行,可以保持它的好的特征如:粒度可伸缩性,同时可以成功地改善它的无损压缩性能.     

AVS无损音频编码标准——熵编码简介

AVS无损音频编码标准,简称AVS-LS,是AVS工作组制定的用于无损压缩音频数据的新标准。AVS-LS采用线性预测和熵编码来对音频数据进行压缩,其中熵编码器用于对线性预测产生的残差信号进行归一化处理及算术编码。介绍了AVS-LS熵编码器的结构及原理,并对AVS-LS的编码效率进行了测试。测试结果表明：AVS-LS的编码效率略低于MPEG-4 ALS,但高于MPEG-4 SLS和FLAC。     

基于聚类的高光谱图像无损压缩

高光谱海量数据的有效压缩成为遥感技术发展中需要迫切解决的问题。该文提出了一种基于聚类的高光谱图像无损压缩算法。针对高光谱图像不同频谱波段间相关性不同的特点,根据相邻波段相关性大小进行波段分组。由于高光谱图像波段数量较多,采用自适应波段选择算法对高光谱图像进行降维,以获取信息量较大的部分波段,利用k均值算法对降维后的波段谱矢量进行聚类。采用多波段预测的方案对各组中的波段进行预测,对于各个分类中的每个像素,分别选取与其空间相邻的已编码的部分同类点进行训练,从而获得当前像素的谱间最优预测系数。对AVIRIS型高光谱图像的实验结果表明,该算法可显著降低压缩后的平均比特率。     

可分级无损音频编码技术的新发展

AAZ（Advanced Audio Zip）是一种基于整数变换的无损音频压缩技术，它能提供从有损到无损的可分级编码，且能与MPEG AAC系统兼容。介绍了AAZ的整体技术框架，并对其关键技术——整数改进离散余弦变换、残差映射和位平面编码作了深入分析，最后与其它无损音频压缩技术在性能上进行了比较，结果表明其具有良好的压缩性能。     

Lossless Digital Watermarking Scheme for Image Maps

A lossless digital watermarking scheme,which was zero- perturbation on the content and graphics for the digital image maps,is proposed.During the simulation,the scheme has been utilized to model the copyright protection program as a commerce application.Compared to the traditional digital watermarking schemes,our scheme operates in redundancy areas of maps and is scalable to topology changes.Experimental results show that,with respect to the geometric attacks and image transformed,the performance of our scheme is better than the classical algorithms based space or frequency domain with much lower complexity..     

无损音频编码标准MPEG-4 ALS

介绍了MPEG-4的音频无损压缩标准草案——MPEG-4 ALS,并且与目前常见的一些无损音频编码算法作比较。     

基于静止图像的小波图像编码

小波图像编码是近十几年发展起来的一种新兴的图像编码方法，目前对其研究较为广泛。主要介绍了当前基于静止图像的小波编码的原理、基本特性、现有方法和发展前景，以及所存在的问题。希望以此进一步推动这一前沿领域的研究工作。     

基于PWM变换器的新型无源无损软开关

详细分析了一种基于PWM变换器的新型无源无损软开关，并给出了其最优化设计步骤。通过一台满载输出功率为900w的带有该无源无损软开关的Boost变换器验证了其开关管实现零电流开通和零电压关断，并与传统的Boost变换器比较，验证其具有较高的效率。     

氢钟频移校准与相位无损切换

为满足VLBI等高精度空间测量技术对时间频率稳定度和准确度提出的更高要求,深空测控系统都配置了高性能的氢原子钟。但由于部件老化、环境变化等影响,氢原子钟输出频率会发生漂移变化,需要对此频移进行校准;同时备份原子钟需要追踪并保持与主钟的输出相位一致,必须进行相位的无损切换才能保障时频信号的连续性。分析了氢原子钟的工作原理和调频移相技术,设计了一种氢钟追踪外部授时系统进行频率漂移校准、主备钟相位无损切换的工程实施方法。应用结果表明,72 h测试时间内,与GPS相比,氢钟的稳定度由原来1.1×10-13提高到3.2×10-14,主备氢钟相位差由原来1.03o减小至0.08o,满足了VLBI长时间高精度测量的精度需求。     

Efficient Level and Zero Coding Methods for H.264/AVC Lossless Intra Coding

Since H.264/AVC was designed mainly for lossy video coding, the entropy coding methods in H.264/AVC are not appropriate for lossless video coding. Based on statistical differences of residual data in lossy and lossless coding, we develop efficient level and zero coding methods. Therefore, we design an improved context-based adaptive variable length coding (CAVLC) scheme for lossless intra coding by modifying the relative entropy coding parts in H.264/AVC. Experimental results show that the proposed method provides approximately 6.8% bit saving, compared with the H.264/AVC FRExt high profile.      

MPEG-4无损音频压缩算法改进

介绍了MPEG-4无损音频压缩标准，并提出了2个改进措施。一是在原有预测器的基础上增加一种新的预测方案以供选择；二是在熵编码中精确搜索最优参数，并引入分组打包机制以更有效地利用编码比特。在运算复杂度增加不多的情况下，压缩效率有明显提高。