Circuitry for decoding huffman codes
First Claim
1. A variable-length decoder system for decoding a variable-length code having a plurality of code values representing variable frequency of occurrence data values and a plurality of differing code prefixes in a variable-length encoded input bit stream, comprising:
- means for determining a first code prefix of said plurality of differing code prefixes in said variable-length encoded input bit stream; and
first code book means having means for determining whether to select a first number of selected bits to be fetched from said variable-length encoded input bit stream in accordance with said first code prefix orto select a second code book means, said second code book means having means for determining a second number of selected bits to be fetched from said variable-length encoded input bit stream in accordance with a second code prefix, wherein said second code prefix is determined from said plurality of differing code prefixes in a variable-length encoded input bit stream after the second code book is selected.
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Abstract
A variable-length decoder system decodes a variable-length code having different code prefixes in an input bit stream. A code prefix is located in the bit stream and used to determine a number of bits to be selected from the input bit stream according to an access of a code book. Additionally, a pointer, directing access to a different code book, may also be indicated by the access of the first code book according to the located code prefix. A determination is made in this decoder system whether to perform the operation of determining a number of bits to be selected from the input stream or accessing a second code prefix table. If the code value is valid, the number of bits is selected and appended to the code prefix to form a code word which is later decoded by the system of the present invention. If another table is indicated a further code prefix is located in the input stream and the further lookup table is accessed in accordance with the further code prefix.
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Citations
11 Claims
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1. A variable-length decoder system for decoding a variable-length code having a plurality of code values representing variable frequency of occurrence data values and a plurality of differing code prefixes in a variable-length encoded input bit stream, comprising:
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means for determining a first code prefix of said plurality of differing code prefixes in said variable-length encoded input bit stream; and first code book means having means for determining whether to select a first number of selected bits to be fetched from said variable-length encoded input bit stream in accordance with said first code prefix or to select a second code book means, said second code book means having means for determining a second number of selected bits to be fetched from said variable-length encoded input bit stream in accordance with a second code prefix, wherein said second code prefix is determined from said plurality of differing code prefixes in a variable-length encoded input bit stream after the second code book is selected. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method for variable-length decoding of a variable-length code having a plurality of code values representing variable frequency of occurrence data values and a plurality of differing code prefixes in a variable-length encoded input bit stream, comprising the steps of:
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(a) determining a first code prefix of said plurality of differing code prefixes in said variable-length encoded input bit stream; and (b) determining whether to select by a first code book means a first number of selected bits to be fetched from said variable-length encoded input bit stream in accordance with said first code prefix or (c) to select a second code book means, said second code book means having means for determining a second number of selected bits to be fetched from said variable-length encoded bit stream in accordance with a second code prefix, wherein said second code prefix is determined from said plurality of differing code prefixes in a variable-length encoded input bit stream after the second code book is selected. - View Dependent Claims (8, 9, 10, 11)
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Specification