Patent Document ID: 7821430
Application ID: 12394132

Base Claim:
1. An arithmetic decoding apparatus that decodes encoded data while updating a first state variable and a second state variable based on a first context variable and a second context variable, the first state variable being a basis for the decoding, the second state variable being an object to be decoded, the first context variable representing a probability state, the second context variable representing a most probable symbol, the arithmetic decoding apparatus comprising: a decoding information table that stores transitions of a range of the most probable symbol and a range of a least probable symbol within a range identified by the first context variable, and a number of a symbol for which the range of the most probable symbol becomes less than a specific value, the decoding information table being referred to based on the first state variable and the first context variable; number-of-symbols determination means for determining the number of symbols in the encoded data that are to be decoded collectively, based on the transitions of the range of the most probable symbol and the range of the least probable symbol, the number of the symbol for which the range of the most probable symbol becomes less than the specific value, and the second state variable; and output means for decoding a symbol corresponding to the number of symbols that are to be decoded collectively, based on the second context variable, and outputting the decoded symbol.

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Claim 2:
2. The arithmetic decoding apparatus according to claim 1 , further comprising decoding information generation means for sequentially generating the range of the most probable symbol and the range of the least probable symbol for a group of continuous symbols that have the same most probable symbol, wherein the decoding information table stores only information that is required to decode a symbol or symbols that follow the group of symbols.