Coded data generation or conversion – Digital code to digital code converters – To or from variable length codes
Patent
1998-02-17
1999-12-28
Young, Brian
Coded data generation or conversion
Digital code to digital code converters
To or from variable length codes
H03M 740
Patent
active
060087455
ABSTRACT:
One embodiment of the present invention provides a method and an apparatus for decoding a variable length code using lookup tables. This embodiment improves lookup performing by allowing multiple symbols to be retrieved in a single lookup, and allowing lookups into different tables to proceed in parallel. Another embodiment of the present invention provides for multiple secondary lookup tables to be selected based upon a prefix value decoded by a primary lookup table. Thus, one embodiment of the present invention can be characterized as an apparatus for decoding a variable length code. This apparatus includes an input from an encoded bitstream, the input including a first set of bits and a second set of bits. This apparatus also includes a first table indexed by the first set of bits, which includes entries containing decoded symbols corresponding to variable length codewords in the first set of bits. At least one entry contains multiple symbols for the case where the first set of bits contains multiple codewords. Another embodiment includes a second table indexed by the second set of bits. This second table includes entries containing decoded symbols corresponding to variable length codewords spanning the first set of bits and the second set of bits. In yet another embodiment, the first table and the second table are configured to allow a lookup from the first table to proceed in parallel with a lookup from the second table. In another embodiment, the first table and the second table are configured so that a lookup in the first table precedes a lookup in the second table.
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patent: 5343195 (1994-08-01), Cooper
patent: 5414468 (1995-05-01), Lee
patent: 5821887 (1998-10-01), Zhu
Noru Krishna K.
Zandi Ahmad
Sun Microsystems Inc.
Young Brian
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