Efficient coding of information: Huffman coding

In his classic paper of 1948, Claude Shannon considered the problem of efficiently describing a source that outputs a sequence of symbols, each associated with a probability of occurrence, and provided the theoretical limits of achievable performance. In 1951, David Huffman presented a technique that attains this performance. This article is a brief overview of some of their results.     

新写作力

在我刊2013年1月(上)中,《中文速读力》一文提出了在互联网时代,中文速读力将是大学生必备的一项能力。除了中文速读力,写作力也是大学生在以后求职、就业中不可缺少的一项能力,而且"写作"范畴也超出传统,包括写作能力+编程能力。     

H．264预测编码关键技术的研究分析

H．264是目前最新的视频编码标准，相对于以前的ITU—T视频编码标准和mpeg序列标准具有更高的压缩效率．编码效率的提高主要归根于精确的帧间预测编码，其中包括多种块模式．多参考帧运动估计和分数像素精度3种新技术的采用，对这些帧间预测编码技术进行研究和分析．主要是分析这些技术与H．264基本配置之间的比较。     

关于算术编码教学的几点注记

随着科学技术的发展,信息、通信类本科生学习信息论是十分必要的。算术编码是基于统计的、无损数据压缩效率最高的编码方法。针对算术编码教学中存在的问题,本文进一步探讨了算术编码的编码、译码过程,提出了编码过程中需要注意的问题,并将算术编码与哈夫曼编码做了比较。最后,用Matlab实现了算术编码的具体实例。     

Categorical color coding by pigeons

Pigeons were trained on two independent tasks. One involved red and yellow hues, the other involved blue and green hues. For half of the birds, the two tasks were the same (i.e., both tasks were either matching-to-sample, or oddity-from-sample). For the remaining birds, the two tasks were different (i.e., one task was matching-to-sample; the other task was oddity-from-sample). Following acquisition, the pigeons were exposed to test trials on which either the correct or the incorrect comparison hue was replaced with one of the hues from the other task. On yellow-sample trials and on green-sample trials, the pigeons performed as if they had a common code for yellow and green. When there was one comparison available that was appropriate to the “yellow/green” code, performance remained high; but when either both comparisons or neither comparison was appropriate to the “yellow/green” code, performance dropped. The pigeons also tended to code red samples as green and to code blue samples as yellow. The results indicate that pigeons can categorically code colors under conditions that rule out a failure to discriminate among the colors.     

一个改进的算术编码算法

Arithmetic coding is the most powerful technique for statiscal lossless encoding that has attracted much attention in recentyears. In this paper, we presents a new implementation of bit-level arithmetic coding by use of integer additions and shifts. The newalgorithm has less computation complexity and is more flexible to use, and thus is very suitable for software and hardware design. Wealso discuss the application of the algorithm to the data encryption.     

Categorical color coding in goldfish

Goldfish, trained in the shuttlebox apparatus to avoid shock, acquired a color discrimination between two colors (red/green) and were tested in transfer with a new set of colors (yellow/blue). Transfer color shock-pairing was either consistent with (red=yellow, blue=green) or opposite to (red≠ yellow, green≠blue) categorical color coding seen in pigeons. Groups with transfer shock-pairing consistent with categorical color coding showed positive transfer, and groups with transfer shock-pairing opposite to categorical color coding showed negative transfer, similar to an attenuated reversal learning effect. These results indicate that goldfish, like pigeons, code different colors as behavioral equivalents even though they can easily learn to discriminate between them. As with pigeons, the finding of the categorical color coding phenomenon changes the conclusions drawn from earlier goldfish conditional-discrimination transfer studies using only signal color changes between acquisition and transfer testing, from evidence of concept learning to evidence for categorical color coding, on the grounds of parsimony. It is important to note that this finding affects only the explanation of conditional-discrimination transfer effects, and the fact remains that both pigeons and goldfish can learn to conditionally discriminate—pigeons for positive reinforcement, and goldfish to avoid shock.     

Dual coding theory and education

Dual coding theory (DCT) explains human behavior and experience in terms of dynamic associative processes that operate on a rich network of modality-specific verbal and nonverbal (or imagery) representations. We first describe the underlying premises of the theory and then show how the basic DCT mechanisms can be used to model diverse educational phenomena. The research demonstrates that concreteness, imagery, and verbal associative processes play major roles in various educational domains: the representation and comprehension of knowledge, learning and memory of school material, effective instruction, individual differences, achievement motivation and test anxiety, and the learning of motor skills. DCT also has important implications for the science and practice of educational psychology — specifically, for educational research and teacher education. We show not only that DCT provides a unified explanation for diverse topics in education, but also that its mechanistic framework accommodates theories cast in terms of strategies and other high-level psychological processes. Although much additional research needs to be done, the concrete models that DCT offers for the behavior and experience of students, teachers, and educational psychologists further our understanding of educational phenomena and strengthen related pedagogical practices.     

Nonlocally centralized simultaneous sparse coding

The concept of structured sparse coding noise is introduced to exploit the spatial correlations and nonlocal constraint of the local structure. Then the model of nonlocally centralized simultaneous sparse coding(NC-SSC) is proposed for reconstructing the original image, and an algorithm is proposed to transform the simultaneous sparse coding into reweighted low-rank approximation. Experimental results on image denoisng, deblurring and super-resolution demonstrate the advantage of the proposed NC-SSC method over the state-of-the-art image restoration methods.     

图像压缩编码的综合分析

介绍了预测编码、变换编码、分形图像编码等几种常用的图像压缩编码方法,在进行系统分析和比较的基础上,指出了各种压缩编码方法的优缺点,阐明了压缩技术未来的技术发展方向和应用发展方向.     

Edge-oriented compression coding on image sequence

１　Ｉｎｔｒｏｄｕｃｔｉｏｎ　Ｉｎｉｍａｇｅｃｏｍｐｒｅｓｓｉｏｎｃｏｄｉｎｇｓｃｈｅｍｅｓ,ｖａｒｉｏｕｓｉｍａｇｅｃｏｄｉｎｇｔｅｃｈｎｉｑｕｅｓｓｕｃｈａｓｔｒａｎｓｆｏｒｍｃｏｄｉｎｇｈａｖｅｂｅｅｎｄｅｖｅｌｏｐｅｄ．Ｗｈｉｌｅｔｈｅｓｅｔｅｃｈｎｉｑｕｅｓｈａｖｅｌｅｄｔｏｒｅｌａｔｉｖｅｌｙｈｉｇｈｑｕａｌｉｔｙｒｅｃｏｎｓｔｒｕｃｔｅｄｉｍａｇｅｓａｔｂｉｔｒａｔｅｓａｒｏｕｎｄ１．０ｂ／ｐｉｘｅｌｏｒｍｏｒｅ,ｔｈｅｙｓｏｍｅｔｉｍｅｓｐｒｏｄｕｃｅｓｐｅｃｉｆｉｃｔｙｐｅｏｆ…     

Pyramid Linear Prediction Coding for Images

lintroductionCompressionofdigitalimagesandvideosignalstoreducetheirstorageandtransmissionbandwidthrequirementsisofgreatinterestintheimplementationofcolnnlunicationsystems.Moreandmorecompressioncodingmethod$fordigitalimagesandvideosignalshavebeenproposedto…     

Multiple descriptions based wavelet image coding

INTRODUCTIONJPEG2 0 0 0 (LawsonandZhu ,2 0 0 2 )isanewlypublishedstillimage codinginternationalstandard .Itsintroductionmeantthatforthefirsttime,thediscretewavelettransform (DWT)wouldbeusedforthedecompositionandrecon structionofimagestogetherwithanefficientcod ingscheme.IntheJPEG2 0 0 0coder,beforeanywaveletdecompositionisperformed ,theimageispartitionedintonon overlappingtiles.Thesetilesareofequalsizeexceptpossiblyforthoseadjacenttotheimageboundary .Thenwavelettransformisappliedtotr…     

改进的基于顶点的形状编码算法

This paper proposes a modified shape coding algorthm called modified vertex-based shape coding(MVBSC) to encode the boundary of a visual object compactly by using a modified polygonal approximation approach which uses modified curvature scale space (CSS) theory to extract feature0points.     

Multipoint videoconferencing with scalable video coding

INTRODUCTION Modern videoconferencing systems allow two o more participants to communicate with each other in real-time using both audio and video. Conventionally when more than two participants are present, a sta configuration is generally employed, wherein a Mul tipoint Conferencing Unit (MCU), or bridge, is util ized to connect to all participants and coordinat communications between them. The general archi tecture is shown in Fig.1. Fig.1 Multipoint videoconferencing system Network…     

Mean shift based log-Gabor wavelet image coding

In this paper, we propose a sparse overcomplete image approximation method based on the ideas of overcomplete log-Gabor wavelet, mean shift and energy concentration. The proposed approximation method selects the necessary wavelet coefficients with a mean shift based algorithm, and concentrates energy on the selected coefficients. It can sparsely approximate the original image, and converges faster than the existing local competition based method. Then, we propose a new compression scheme based on the above approximation method. The scheme has compression performance similar to JPEG 2000. The images decoded with the proposed compression scheme appear more pleasant to the human eyes than those with JPEG 2000.