Patent ID: 8014617

Claim:
A decoding apparatus comprising: a distribution estimating section that estimates distribution of original data corresponding to quantization indexes executed by a controller, comprising: a frequency distribution measuring section that measures a frequency distribution based on the quantization indexes and acquires a maximum value of absolute values of the quantization indexes qM; a histogram normalizing section that normalizes the frequency distribution measured by the frequency distribution measuring section and generates a normalized histogram; a preset value acquiring section that determines the preset value based on the maximum value of absolute values of the quantization indexes acquired by the frequency distribution measuring section; and a standard-deviation estimating section that calculates a standard deviation using an equation: σ = - ( 2 ⁢ N + 1 ) ⁢ D 2 ⁢ log ⁡ [ 1 - ∑ q = - N N ⁢ H ⁡ ( q ) ] , wherein σ is the standard deviation, N is the preset value, H(q) is the normalized histogram, q is the quantization indexes and D is a quantization step size.