Showing papers on "Lossless compression published in 1983"

A universal data compression system

Abstract: A universal data compression algorithm is described which is capable of compressing long strings generated by a "finitely generated" source, with a near optimum per symbol length without prior knowledge of the source. This class of sources may be viewed as a generalization of Markov sources to random fields. Moreover, the algorithm does not require a working storage much larger than that needed to describe the source generating parameters.

Is text compression by prefixes and suffixes practical

Abstract: One approach to text compression is to replace high-frequency variable-length fragments of words by fixed-length codes pointing to a compression table containing these high-frequency fragments. It is shown that the problem of optimal fragment compression is NP-hard even if the fragments are restricted to prefixes and suffixes. This seems to be a simplest fragment compression problem which is NP-hard, since a polynomial algorithm for compressing by prefixes only (or suffixes only) has been found recently. Various compression heuristics based on using both prefixes and suffixes have been tested on large Hebrew and English texts. The best of these heuristics produce a net compression of some 37% for Hebrew and 45% for English using a prefix/suffix compression table of size 256.

Alternate line interpolation method and apparatus

Abstract: A method and apparatus are provided for data compression in a digital facile document transmission system. In accordance with the method, only alternate scan lines are transmitted, i.e., every other line is deleted in transmission, and at the receiver, the missing scan lines are interpolated from the transmitted data. This compression technique provides a fixed compression ratio of 2 to 1 regardless of the complexity of the input document. The interpolation method relies on comparing, for each picture element to be interpolated, the colors of one or more pairs of adjacent picture elements of the transmitted scan lines and making a decision as to the color of the picture element to be interpolated on this basis.

A new approach for synthesis of low sensitivity digital filter structures based on lossless building blocks

Abstract: In a recent paper [1], it is shown that a fundamental requirement for low passband sensitivity realization of a digital transfer function is that the implementation be structurally passive, or bounded. In this paper, a general procedure for developing low-sensitivity realizations of a transfer function is advanced. The resulting structures are in the form of a cascade connection of basic digital two-pair structures satisfying a "lossless" property in the z-domain. The methods advanced here cover the well-known wave digital filters and the Gray-Markel lattices as special cases. The synthesis procedure is entirely z-domain based, and does not make reference to continuous time networks, unlike the wave digital filters which are designed starting from a continuous time network.