Patent ID: 7830284

Claim:
An entropy encoding apparatus comprising: a binarization unit configured to convert an input syntax element into binarized data; a context calculation unit configured to generate a context index used to identify context information for each bit of the binarized data; a context memory unit configured to hold context information; and an arithmetic coding unit configured to perform arithmetic coding using context information output from said context memory unit corresponding to the generated context index, and the binarized data, wherein said context memory unit comprises: a storage unit configured to hold context information, an initial value generation unit configured to generate an initial value of context information based on the generated context index, a control unit configured to output a control signal specifying which to select between the initial value and the context information which, being held in said storage unit, corresponds to the generated context index, a selection unit configured to select either of the initial value or the context information which corresponds to the generated context index, based on the control signal, and output selected context information which contains most probable symbol and probability state index, an updating unit configured to receive the selected context information and the binarized data, compare a value of the binarized data and a value of the most probable symbol contained in the selected context information, and generate updated context information based on a comparison result between the compared two values, wherein when the compared two values are not equal, said updating unit generates the updated context information in which a value of the probability state index contained in the selected context information is updated according to a predetermined table, and output the updated context information to said arithmetic coding unit and said storage unit so that said storage unit holds the updated context information associating with the generated context index.