Showing papers on "Lossless compression published in 1982"

File archival techniques using data compression

Abstract: The performance of most small computer systems is determined, to a large extent, by the characteristics of their mass storage devices. Data compression can expand the storage capacity of such devices and also slightly increase their speed. Here, a summary of one method of data compression using Huffman variable length coding is presented, along with statistics of effectiveness for various file types and practical techniques for integrating such methods into a small computer system.

A multi-group technique for data compression

Abstract: An efficient compression technique that is particularly attractive for the storage of large commercial files and the transfer of such files within a distributed communication network is outlined. The technique, constructed as a two-level hierarchy of Huffman-type binary trees, is a reversible semantic-independent variable-length character encoding method that makes use of the group locality of character reference behavior and the variable frequency of occurrence of various characters within the different subgroupings of the character set. The compression efficiency and cost of the Multi-Group scheme has been found to be superior to the well-known Huffman encoding algorithm.

Computer‐Aided partial synthesis of lossless non‐uniform lines of finite length

Abstract: A computer-aided method for solving the problem of partial or one-parameter synthesis of a lossless non-uniform transmission line of finite length is presented. This method is essentially the same as the pulse-spectrum technique for solving the inverse problems of determining the velocity coefficients of the wave equation from known information of the solution on the boundary. The basic idea of this method is that the original synthesis problem in the time-domain is first reduced to a CW synthesis problem in the frequency-domain, by either Fourier transform or Laplace transform, and then the synthesis is carried out in the frequency-domain by using an iterative numerical algorithm. Numerical simulations are carried out to test the feasibility and to study the general performance of this computer-aided synthesis procedure without the real design data. It is found that this computer-aided method does give excellent results.

Reversible seismic data compression

Abstract: This paper is concerned with reversible seismic data compression techniques for transmitting data from exploration field to a research center via satellite. The statistical character istics of seismic data, including Vibroseis data and impulsive data, are examined. Based on these characteristics, various compression techniques, including prediction, orthogonal transforms, and digital coding methods have been investigated. Explicit methods are proposed for compressing the Vibroseis and impulsive data. These methods have been simulated for extensive real data. The compression performance is measured by the compression ratio and the signal-to-noise ratio. The results indicate that a compression ratio ranging between five to one and six to one with at least a 30 dB SNR can be achieved. Facts of real-time design that is, execution time, core size requirement, depth of queue, and transmission time are examined. For transmitting the compressed seismic data using a 7-bit block counter with continuous ARQ, 5000 bits per frame are recommended for a 9600 bps channel bandwidth.

On a Class of Linear Maps for Data Compression

Abstract: A method for data compression with linear maps has been developed which is found to produce further reduction in overhead storage requirement, compression/decompression time, and clustering overhead as compared to the affine map method in certain cases. Algorithms have been developed for cluster minimization, cluster identification, and compression matrix calculation that may be applied with advantage in both the methods.