Method and apparatus for decompressing encoded data

Details Method and apparatus for decompressing encoded data Method and apparatus for decompressing encoded data

1987-06-10

1989-02-28

Coles, Sr., Edward L.

Facsimile and static presentation processing

Facsimile

Recording apparatus

3582613, 341 59, H04N 1417

Patent

active

048090816

ABSTRACT:
A fast and flexible data decompressor decodes data, such as that encoded by CCITT Group 4 facsimile machines, to produce display data. In the decompressor, a microprocessor controlled by microcode evaluates variable length codes each representing a series of data cells, each data cell in a series having a single value assigned thereto. The variable length codes have a first code type, such as vertical codes and pass codes used in two-dimensional coding schemes, are decoded by the microprocessor. The variable length codes having a second type, such as one-dimensional horizontal codes, are decoded by a pair of loo k-up tables in read only memories (ROM's). One ROM determines the length of the code and the other determines the run length of the series of data cells represented by the code. A shifter which receives encoded data is shifted by the length of the code, whether determined by the code length ROM or the microprocessor. The microprocessor generates an intermediate code indicating the run length and the single value to be assigned to each of the data cells in the series of data cells, using the run length from the run length ROM if the code is of the second type. The intermediate code is sent to a bit generator which generates a series of bits corresponding to the data cells.

REFERENCES:
patent: 4578704 (1986-03-01), Gharavi
patent: 4626921 (1986-12-01), Ohtani et al.
patent: 4654719 (1987-03-01), Tomita
patent: 4677649 (1987-06-01), Kunishi et al.
patent: 4729034 (1988-03-01), Roberts et al.

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