To provide a quantization step parameter decision apparatus, a quantization step parameter decision method, a quantization step parameter decision program whereby the number of quantization processing times can be decreased and to provide a nonlinear quantization method, a nonlinear quantization apparatus, and a nonlinear quantization program whereby upsizing of the circuit scale can be suppressed and high speed processing can be attained.

The quantization step parameter decision apparatus 1 for calculating the quantization step parameter for a nonlinear quantization apparatus is provided with: a quantization means 2 for performing quantization by the quantization step parameter of a preceding granule; a comparison means 3 for comparing the number of bits being a value obtained by the quantization means 2 with the specified number of bits; a same time processing means 4 for adopting the quantization step parameter when the number of bits is the same as the specified number of bits as a result of the comparison; a greater state processing means 5 for incrementing the quantization step parameter one by one each to obtain and adopt a maximum value of the specified number of bits or below when the number of bits is greater than the specified number of bits as a result of the comparison; and a smaller state processing means 6 for decreasing the quantization step parameter to obtain a maximum value being the specified number of bits or below and to adopt it when the number of bits is smaller than the specified number of bits as a result of the comparison.