Coded data generation or conversion – Digital code to digital code converters – To or from code based on probability
Patent
1994-02-23
1995-11-28
Williams, Howard L.
Coded data generation or conversion
Digital code to digital code converters
To or from code based on probability
341 51, 382232, H03M 730
Patent
active
054712076
ABSTRACT:
The invention provides an improved method and apparatus for compression of palettized images. Input symbols in an M-ary alphabet are binarized based on a context model of the input data, where the binarization is selected to provide good compression by a binary encoder. The particular binarization is determined from a reindexing table which maps each input symbol to a number of binary values. The mapping is determined from the images to be compressed, and is typically transmitted with the compressed images as overhead. The mapping is a local minimum of the bitwise entropy of the binarization. With or without reindexing the input, the symbols can be converted compressed in parallel, with the bits of the input symbols buffered and reordered as necessary to ensure that bits needed for context of a bit being decoded are available before the decompressor decodes the bit being decoded. The decompressor includes a means for performing the opposite reordering such that the output of the decompressor is the same as the input to the compressor.
REFERENCES:
patent: 5095374 (1992-03-01), Klein et al.
patent: 5297220 (1994-03-01), Nomizu
patent: 5349348 (1994-09-01), Anderson et al.
H. Gharavi, "Conditional Entropy Coding of Digital Pictures," Journal of IRE, vol. 56, No. 5, pp. 213-218, May, 1986.
IBM Technical Disclosure Bulletin, vol. 35, No. 7, Dec. 1992, pp. 315-316.
Y. Chin, et al., "Lossy Compression of Palettized Images", ICASSP-93, vol. V, pp. 325-328.
Allen James
Stork David G.
Zandi Ahmad
Albert Philip H.
Ricoh & Company, Ltd.
Ricoh Corporation
Williams Howard L.
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