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     

Xilinx哈夫曼编码系统设计

在图像处理、文件传真、视频压缩编码中,哈夫曼编码是最常用的一种编码方式.本文设计并实现了对一段数字序列进行哈夫曼编码并将编码结果串行输出的电路模块,电路由输入数据的排序、数据的哈夫曼编码、数据序列编码的结果输出三个核心模块组成,在Xilinx平台上通过硬件描述语言实现该电路.仿真结果表明,该电路编码正确,并具有较高的工作频率和编码效率.     

基于JPEG图像解码的高速Huffman解码电路

研究JPEG图像的Huffman解码器在集成电路上的实现问题,以范式Huffman编码为研究对象,在研究范式Huffman编码特点及快速算法的基础上设计出高速Huffman解码电路。此解码电路已经在Altera的FPGA上通过测试,系统能稳定运行在140 MHz,输出数据平均达到约1.2 Gb/s的带宽。     

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     

改进的Huffman编码及其应用

该文探讨了JPEG压缩技术，重点针对Huffman编码中最优二叉树的“形态”不唯一问题，提出一种基于“简单原则”的新方法。经过这种方法改进的Huffman编码，使得JPEG中相应的值或字符的Huffman编码是唯一的。与传统的Huffman算法及近年来国内外文献中提出的改进算法相比，该方法编码步骤和相关操作更简洁，因而更利于程序的实现和移植。最后给出一个实例，表明此方法的实用性。     

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     

Interference Blanker for Dissimilar Modified Huffman Sequences

There are many pulse-coded sequence solutions for a pulse compression design that are available from D. A. Huffman's polynomial approach. If a sequence of length 13 is considered then there are 122 independent sequence solutions for the autocorrelation function of design. Out of this diversity of possible solutions some will be usable because pulse train energy utilization is high. The components of any chosen sequence possess different amplitude and phase excitation values which could be implemented by today's technology. In this paper an "interference blanker" is defined as a device that permits simultaneous operation of two or more pulse compression equipments so that there is no suppression of range resolution accuracy. The pulse compression decoder for the modified D. A. Huffman impulse-equivalent pulse trains is shown to be an " interference blanker" because the cross-correlation function between any two usable sequence solutions shows great variation from the autocorrelation function of design. Because in a practical implementation, there is a limit to the time sidelobe reduction that can be accomplished, D. A. Huffman's zero time sidelobe condition is modified. As an example, the ten most favorable sequence solutions for the time sidelobe level of 32.3 dB and a sequence length 13 are studied.     

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     

A Modified Huffman Procedure with Reduced Memory Requirement

The usual Huffman procedure for source coding requires a codebook memory for translation of the source messages into variable-length codewords. When some of the source messages are highly improbable, the size of the required codebook becomes very large. This correspondence proposes a modification of the Huffman procedure to reduce the size of the required memory under those conditions.     

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。     

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FPGA的JPEG编解码设计

JPEG(Joint Photographic Experts Group)作为一个基本的图像压缩方式,已经得到了广泛的运用。而FPGA具有的并行计算特点,使得越来越多的设备利用FPGA对jpeg文件进行编解码。从整体上介绍JPEG编解码的基本算法,并着重介绍了在DCT和Huffman两个模块中使用的方法。在DCT/IDCT模块中,为了提高处理速度,充分利用FPGA并行处理的特点。对于Huffman解码模块,采用附加码位宽的查找表方法,并利用综合工具将查找表综合到片内存储器中这一特点来减少资源。     

On RD optimized progressive image coding using JPEG

Among the many different modes of operations allowed in the current JPEG standard, the sequential and progressive modes are the most widely used. While the sequential JPEG mode yields essentially the same level of compression performance for most encoder implementations, the performance of progressive JPEG depends highly upon the designed encoder structure. This is due to the flexibility the standard leaves open in designing progressive JPEG encoders. In this work, a rate-distortion (RD) optimized JPEG compliant progressive encoder is presented that produces a sequence of scans, ordered in terms of decreasing importance. Our encoder outperforms an optimized sequential JPEG encoder in terms of compression efficiency, substantially at low and high bit rates. Moreover, unlike existing JPEG compliant encoders, our encoder can achieve precise rate/distortion control. Substantially better compression performance and precise rate control, provided by our progressive JPEG compliant encoding algorithm, are two highly desired features currently sought for the emerging JPEG-2000 standard.     

Concurrency techniques for arithmetic coding in JPEG2000

JPEG2000 is a recently standardized image compression algorithm. The heart of this algorithm is the coding scheme known as embedded block coding with optimal truncation (EBCOT). This contributes the majority of processing time to the compression algorithm. The EBCOT scheme consists of a bit-plane coder coupled to a MQ arithmetic coder. Recent bit-plane coder architectures are capable of producing symbols at a higher rate than the existing MQ arithmetic coders can absorb. Thus, there is a requirement for a high throughput MQ arithmetic coder. We examine the existing MQ arithmetic coder architectures and develop novel techniques capable of absorbing the high symbol rate from high performance bit-plane coders, as well as providing flexible design choices.     

基于FPGA的JPEG编解码设计

JPEG（Joint Photographic Experts Group）作为一个基本的图像压缩方式,已经得到了广泛的运用。而FPGA具有的并行计算特点,使得越来越多的设备利用FPGA对jpeg文件进行编解码。从整体上介绍JPEG编解码的基本算法,并着重介绍了在DCT和Huffman两个模块中使用的方法。在DCT／IDCT模块中,为了提高处理速度,充分利用FPGA并行处理的特点。对于Huff-man解码模块,采用附加码位宽的查找表方法,并利用综合工具将查找表综合到片内存储器中这一特点来减少资源。     

Classified JPEG coding of mixed document images for printing

This paper presents a modified JPEG coder that is applied to the compression of mixed documents (containing text, natural images, and graphics) for printing purposes. The modified JPEG coder proposed in this paper takes advantage of the distinct perceptually significant regions in these documents to achieve higher perceptual quality than the standard JPEG coder. The region-adaptivity is performed via classified thresholding being totally compliant with the baseline standard. A computationally efficient classification algorithm is presented, and the improved performance of the classified JPEG coder is verified.     

Significant bit-plane clustering technique for JPEG2000 image coding

The bit-plane clustering technique is applied to high-energy code blocks to enhance the energy compaction by rearranging the column positions in these code blocks. The energy compaction effect can improve the coding efficiency of JPEG2000, which results in an improvement of 6.88% bit-rate reduction at 0.1 bpp on average over JPEG2000.