主题变奏曲：手持游戏系统的激增、不同特色的兜售及价目标签

娱乐控制台正在追随计算机的足迹,大踏步地进入移动领域。在竟争的早期阶段,对完美系统的定义是见仁见智,从而导致了产品的多样性。     

On breaking a Huffman code

We examine the problem of deciphering a file that has been Huffman coded, but not otherwise encrypted. We find that a Huffman code can be surprisingly difficult to cryptanalyze. We present a detailed analysis of the situation for a three-symbol source alphabet and present some results for general finite alphabets     

一种高效哈夫曼解码器的设计与实现

本文介绍了一种高效、高速哈夫曼解码器的设计与实现。这种解码器的解码算法是建立在一种对哈夫曼树结构的特殊分类的基础上的。这种方法极大地降低了存储哈夫曼表所用的存储器大小,并且提高了查找的速度。     

The length of a typical Huffman codeword

If p_i(i=1,···, N) is the probability of the ith letter of a memoryless source, the length l_i of the corresponding binary Huffman codeword can be very different from the value -log p_i. For a typical letter, however, l_i≈-logp_i. More precisely, P_m ^-=Σ/sub j∈{i|l<-logpj-m}/p_j<2^-m and P_m ⁺=Σ/sub j∈{i|li>-logpi+m/}p_j<2^-c(m-2)+2, where c≈2.27     

Complementary Huffman sequences

The theories of complementary and Huffman sequences have been two distinct areas. It is shown that each Huffman sequence has its complementary pair. In radar applications, these pairs can be used, in the same way as other binary and nonbinary complementary sequences. They have the added advantage of zero autocorrelation sidelobes at all time shifts except the largest one. Even these sidelobes are cancelled if the autocorrelation functions are summed because of the complementarity.<>     

Level-compressed Huffman decoding

Based on the breadth-first search manner and the level-compression technique, this article first presents a new array data structure to represent the classical Huffman (1952) tree. Then, the decoding algorithm is given. Both the memory and the decoding time required in the proposed method are less than those of previous methods. Some experimentations are carried out to demonstrate the advantages of the proposed method. In fact, the proposed algorithm can be applied to the canonical Huffman tree     

Effect on Speech Compression by Combined Delta Encoding and Huffman Coding Scheme

This paper reports the effect of compression by applying delta encoding and Huffman coding schemes together on speech signals of American-English and Hindi from International Phonetic Alphabet database. First of all, these speech signals have been delta encoded and then compressed by Huffman coding. By doing so, it has been observed here that the Huffman coding gives high compression ratio for this delta encoded speech signals as compared to the compression on the input speech signals only incorporating Huffman coding.     

Huffman codes and self-information

In this paper the connection between the self-information of a source letter from a finite alphabet and its code-word length in a Huffman code is investigated. Consider the set of all independent finite alphabet sources which contain a source letter a of probabilityp. The maximum over this set of the length of a Huffman codeword for a is determined. This maximum remains constant aspvaries between the reciprocal values of two consecutive Fibonacci numbers. For the smallpthis maximum is approximately equal toleft[ log_{2} frac{1+ sqrt{5}}{2} right]^{-1} approx 1.44times the self-information.     

Modified JPEG Huffman coding

It is a well observed characteristic that when a DCT block is traversed in the zigzag order, the AC coefficients generally decrease in size and the run-length of zero coefficients increase in number. This article presents a minor modification to the Huffman coding of the JPEG baseline compression algorithm to exploit this redundancy. For this purpose, DCT blocks are divided into bands so that each band can be coded using a separate code table. Three implementations are presented, which all move the end-of-block marker up in the middle of DCT block and use it to indicate the band boundaries. Experimental results are presented to compare reduction in the code size obtained by our methods with the JPEG sequential-mode Huffman coding and arithmetic coding methods. The average code reduction to the total image code size of one of our methods is 4%. Our methods can also be used for progressive image transmission and hence, experimental results are also given to compare them with two-, three-, and four-band implementations of the JPEG spectral selection method.     

Multilevel aperiodic Huffman sequences

Certain sequences that have zero aperiodic autocorrelation except for zero and the maximum shifts are described. They are useful in radar pulse compression.     

并行哈夫曼编码器的硬件设计与实现

文章设计了一种并行编码的哈夫曼硬件编码器，它采用了流水线和并行编码方法，使得在一个时钟周期内可以编码一个字节的数据，在编码时显著降低了工作频率。文章给出了关键部分的实现方案并分析了实验结果。     

Tight bounds on the redundancy of Huffman codes

A method for deriving optimal upper bounds on the redundancy of binary Huffman codes in terms of the probability p₁ of the most likely source letter is presented. This method will be used to compute bounds for all p₁⩾1/127, which were previously known only for a few special cases. Furthermore, the known optimal lower bound for binary Huffman codes is generalized to arbitrary code alphabets and some upper bounds for D-ary Huffman codes, 2⩽D<∞, are given, which are the tightest possible for all p₁⩾1/2     

A fast-adaptive Huffman coding algorithm

The Huffman code in practice suffers from two problems: the prior knowledge of the probability distribution of the data source to be encoded is necessary, and the encoded data propagate errors. The first problem can be solved by adaptive coding, while the second problem can be partly solved by segmenting data into segments. However, the adaptive Huffman code performs badly when segmenting data into relatively small segments because of its relatively slow adaptability. A fast-adaptive coding algorithm which tracks the local data statistics more quickly, thus yielding better compression efficiency, is given     

Low power parallel Huffman decoding

A low power design technique for a parallel Huffman decoder is presented. According to the length of the incoming Huffman codeword, the proposed strategy makes the barrel shifter in the parallel Huffman decoder turn off the unnecessary shifting bits to reduce power dissipation. The result of a SPICE simulation indicates that up to 50 percent power reduction in the barrel shifter may be achieved with the proposed technique     

Parallelized Huffman and Hu-Tucker searching

Forests constructed by the binary Huffman (1952) and Hu-Tucker (1971) algorithms solve parallelized search problems. Bounds on the resulting minimum average search lengths for items occurring with given probabilities are established     

高速Huffman解码器设计与实现

本文设计了一种新的Ｈｕｆｆｍａｎ解码器的算法，它不仅能够减少常规算法对存储空间的要求，更为重要的是它能够在一个进钟节拍中和多个数据，具有明显的优点，最后以ＪＰＥＧ为例描述了它的ＶＬＳＩ实现方案。     

An improvement of dynamic Huffman coding with a simple repetitionfinder

A mixed-mode file compression scheme that incorporates interval encoding for finding duplicate occurrences of strings without storing or parsing the past sequence and a one-pass scheme for dynamic Huffman codes is presented. Results from experiments performed on various types of files are discussed. The proposed method runs in linear time, and the memory requirement depends only on the alphabet size. The code efficiency is compared experimentally to that of other schemes     

基于Matlab文本文件哈夫曼编解码仿真

根据当前数据压缩技术的现状,论述了Huffman可变长压缩的编解码方法。为了验证Huffman编解码的具体过程和特点,采用Matlab软件编程仿真的方法,将优先队列转成二叉树并建立编码和解码的字典表。对一随机英文文本文件进行了Huffman编解码仿真,得到了各个字母的概率、码字、平均信息量、平均长度、冗余度以及编码解码序列输出,具有明确的压缩特点。     

基于verilog实现哈夫曼编码的新方法

传统的硬件实现哈夫曼编码的方法主要有:预先构造哈夫曼编码表,编码器通过查表的方法输出哈夫曼编码[1];编码器动态生成哈夫曼树,通过遍历节点方式获取哈夫曼编码[2-3].第一种方法从平均码长角度看,在很多情况下非最优;第二种方法需要生成完整的哈夫曼树,会产生大量的节点,且需遍历哈夫曼树获取哈夫曼编码,资源占用多,实现较为麻烦.本文基于软件实现[4]时,使用哈夫曼树,会提出一种适用于硬件并行实现的新数据结构——字符池,通过对字符池的频数属性比较和排序来决定各个字符节点在字符池中的归属.配置字符池的同时逐步生成哈夫曼编码,可以提高硬件利用率,并且无需额外操作来提取哈夫曼编码.