Showing papers on "Run-length encoding published in 1973"

Graphic data redundancy reduction for text and half-tone optical facsimile system

Abstract: A text and half-tone facsimile system employing graphic data redundancy reduction allowing faster transmission over a communication line of fixed capacity or preservation of transmission time over a communication line of lower capacity. Reduction is achieved by scanning a document to be transmitted at a constant rate with an optical facsimile system and storing the highly variable rate of graphic information generated from the black and white contents of the scanned document in memory storage devices, one memory device for each scan line. The stored graphic data is then processed at a highly variable rate from more than one adjacent scan line at a time by selection logic circuitry which automatically switches the resolution for compressing data from more than one line at a time when the resolution is low (high resolution for half-tone and low resolution for type). In addition, the data is further compressed by run length encoding. The processing rate of the graphic data is automatically determined so as to maintain a nearly constant data transmission rate, thus utilizing the full capacity of the transmission line.

Data compression techniques as a means of reducing the storage requirements for satellite data: a quantitative comparison

Abstract: This paper reports on an investigation into the application of data compression techniques as a means of reducing the ‘on-ground’ data storage requirements that are associated with many space research programmes. The paper presents and compares quantitatively various compression techniques based on the Shannon-Fano, ‘run-length’ and Hadamard transformation methods of source encoding. The compression ratios obtained when applying the techniques to actual satellite data are given and some new basic theory relating to ‘run-length’ encoding is presented.