Performance-based reset of data compression dictionary

Details Performance-based reset of data compression dictionary Performance-based reset of data compression dictionary

1987-10-19

1989-07-11

Shoop, Jr., William M.

Coded data generation or conversion

Digital code to digital code converters

Coding by table look-up techniques

341 51, 341 59, 358261, H03M 746

Patent

active

048476196

ABSTRACT:
An adaptive data compression system is reset when performance drops below a predetermined threshold to permit greater compression of long files with evolving distributions of symbol combinations. The compression system uses a resettable dictionary in which initially unassigned codes are strategically assigned to symbol combinations as they are encountered in the data stream.
The difference between the bit-lengths of corresponding lengths of the compressor input and output is compared with a value representing a predetermined performance threshold. The dictionary can be reset if the actual performance falls below the performance threshold. The reset can be inhibited while the dictionary is less than half-full to ensure that performance measures are statistically significant. However, if the performance is such that data expansion is occurring, reset is not so delayed.

REFERENCES:
patent: 3906485 (1975-09-01), Hong et al.
patent: 4387364 (1983-06-01), Shirota
patent: 4464650 (1984-08-01), Eastman et al.
patent: 4558302 (1985-12-01), Welch
patent: 4586027 (1986-04-01), Tsukiyama et al.
patent: 4609907 (1986-09-01), Adler et al.

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