游程编码与哈夫曼编码联合压缩实现技术

随着海量数据进入我们的生活,数据压缩成为计算机科学领域中十分活跃的论题,游程编码与哈夫曼编码是两种典型的无损压缩编码的方法,通过对两种编码压缩思想的分析,并对游程编码算法进行改进,将两者联合起来进行数据压缩,以期达到更大压缩比的目的。     

哈夫曼编码在图像压缩中的应用与分析

互联网发展以来,在信息传递的过程中,难免会存在由于文件内存占用过大,导致传输效率低下,网络延迟等,因此文件压缩、图像压缩等技术也逐渐应用于日常生活中。文章以哈夫曼编码为主要编码思想,通过C++语言对编码算法进行实现,从而对图像压缩的相关技术进行研究,通过哈夫曼编码实现对图像的压缩和对比分析。     

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。     

基于概率补偿的无哈夫曼树变长压缩编码

现在广泛使用的压缩编码方法都要通过哈夫曼树来实现,这样围绕着哈夫曼树就存在着许多运算过程.为了化简编码过程,提出了一种无需哈夫曼树就能实现的变长最佳编码方法,通过一个概率补偿的过程,可以直接得到所有信源的最佳码长.知道码长和概率后也无需通过哈夫曼树就可以确定最后的编码,并且可以证明结果满足变长最佳编码定理和前缀编码.经测试,该方法可以快速有效得到变长最佳编码,并简化了变长编码的运算存储过程.     

哈夫曼编码方法的方案选择研究

本文首先分析了哈夫曼编码的理论根据,介绍了哈夫曼编码的编码过程,通过举例详细分析了不同编码方案的编码结果,最后对不同方案的编码方法进行了总结。     

哈夫曼算法在图像压缩中的具体实现及改进

哈夫曼编码作为一种最常用无损压缩编码方法，在数据压缩程序中具有非常重要的应用。本文对哈夫曼编码算法进行了全面的探讨，给出了具体的压缩及解压缩过程及程序，并结合数字图像的特点对绘出的算法讨论，提出一些改进。     

基于改进哈夫曼编码的大规模动态图可达查询方法

随着社交网络分析、生物信息网络分析等新兴应用的涌现和计算机技术的飞速发展,图的规模迅速增长,并且频繁更新,使得对大规模动态图数据的处理需求愈加迫切.现有的面向大规模动态图的可达查询研究成果较少,尚存在索引压缩困难以及图结构待优化等问题.本文提出了一种支持大规模动态图的基于改进哈夫曼编码的可达查询处理方法（Huffman-based Label Reachability,HuffLR）.该方法首先对预处理图进行结构上的两次压缩,得到双压缩图;其次,基于双压缩图提出一种前缀label索引,该索引能够有效表达节点间的可达关系;最后,提出双压缩图的演进和可达查询处理及优化算法,主要包括边的插入与删除、节点的插入与删除.实验表明,本文提出的基于改进哈夫曼编码的大规模动态图可达查询处理方法具有良好的可行性和有效性.     

哈夫曼编码及在数字电视广播中的应用

简要介绍了最优二叉树,哈夫曼编码的来历,哈夫曼编码原理以及哈夫曼编码在数字电视系统信源编码中的应用情况。     

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.     

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     

Huffman coding with an infinite alphabet

A new type of sufficient condition is provided for a probability distribution on the nonnegative integers to be given an optimal D-ary prefix code by a Huffman-type algorithm. In the justification of our algorithm, we introduce two new (essentially one) concepts as the definition of the “optimality” of a prefix D-ary code, which are shown to be equivalent to that defined in the traditional way. These new concepts of the optimality are meaningful even for the case where the Shannon entropy H(P) diverges     

基于Xilinx MicroBlaze多核嵌入式系统的设计

MicroBlaze核是嵌入在Xilinx FPGA之中的属于32位RISC Harvard架构软处理器核。针对Xilinx MicroBlaze软处理器的核间互连,实现多处理器核之间的快速通信的目的,采用了PLB和FSL总线混连的方法,利用xps_mail-box和xps_mutex核完成核间的通信与同步,通过在Xilinx EDK平台下,将3个软处理器核嵌入到FPGA Spartan-3E芯片上的试验,开发出了一个运行在FPGA上的基于多处理器的嵌入式可编程片上系统,得出此种多核处理器混连的可行性与实用性,核间通信速度得到提升的结论。     

Memory efficient and high-speed search Huffman coding

Code compression is a key element in high-speed digital data transport. A major compression is performed by converting the fixed-length codes to variable-length codes through a (semi-)entropy coding scheme. Huffman coding is shown to be a very efficient coding scheme. To speed up the process of search for a symbol in a Huffman tree and to reduce the memory size we have proposed a tree clustering algorithm to avoid high sparsity of the tree. The method is shown to be extremely efficient in memory requirement, and fast in searching for the symbol. For an experimental video data with Huffman codes extended up to 13 bits in length, the entire memory space is shown to be 122 words, compared to 2¹³=8192 words in a normal situation     

Memory allocation for Huffman coding of multiple sources

The authors propose an efficient memory allocation method for memory-constrained Huffman coding of multiple sources which employs the iterative bisection algorithm. The proposed method provides better performance over conventional allocation methods and can be applied to many adaptive variable-length coders with memory constraints     

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.     

An efficient repetition finder for improving dynamic Huffman coding

In this paper, a new repetition finder to be used with dynamic Huffman (1952) coding is proposed to improve the compression efficiency by reducing the redundancy due to string repetitions. Compared to the repetition finder proposed by Yokoo (1991), the proposed scheme effectively increases the numbers of consecutive symbols in the repetition mode and the total number of symbols in the repetition mode. Experimental results show that the proposed method outperforms the repetition finder of Yokoo by 14-40% in compression ratios with about the same memory requirement and running time     

多进制霍夫曼编码方法及最优性证明

信源编码最常用的翟夫曼可变长编码是性能最优的唯一可译即时码。在讨论编码方法时常以二进制为例进行。多进制的霍夫曼编码如何进行,怎样证明得到的编码一定是平均码长最短的唯一可译即时码,是本文讨论和证明的主题。