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Overlapped Statistics Memory Access for Decompression Disclosure Number: IPCOM000042996D
Original Publication Date: 1984-Jun-01
Included in the Prior Art Database: 2005-Feb-04

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Highbarger, ST Langdon, GG [+details]


This invention relates to an apparatus for increasing the arithmetic encoding/decoding throughput. The increase is obtained by the concurrent accessing of a multi-ported RAM (random-access memory) for obtaining necessary statistical coding data on a lookahead basis. The binary coding methods for file compaction require statistics on the frequency of occurrence of patterns in bit streams in order to achieve compression. This entails the fetching of a statistic for each encoded or decoded bit. This requirement for providing a statistic on a bit basis represents a speed constraint. The statistics termed a skew are stored in a linearized tree arrangement of data. The requirement for coding a byte is to access each level of the tree only once every eight bits encoded.