Patent ID: 7688234

Claim:
A coding apparatus, comprising: an orthogonal transformation unit that applies an orthogonal transformation to an input signal and outputs the resulting coefficient data; a quantizer that quantizes the coefficient data; an arithmetic coder that performs arithmetic coding on the output data from the quantizer and outputs the resulting coded data; and a controller that executes rate control processing to control the quantization scale of the quantizer; wherein the arithmetic coder includes a binarization unit that converts the output data from the quantizer into binary symbols, a binary arithmetic coder that performs binary arithmetic coding on the binary symbols and outputs the resulting coded data, and a code length predictor that outputs a predicted number of bits in the coded data on the basis of the bin size of the binary symbols, the controller executes rate control processing to control the quantization scale of the quantizer on the basis of the predicted number of bits, the code length predictor outputs the predicted number of bits by evaluating a predefined predictive function using the bin size as the argument of the function, and the predictive function is a polynomial function defined such that the predicted number of bits increases as the bin size increases, and furthermore such that the polynomial degree of the function changes when the bin size exceeds a predefined threshold value.