Patent ID: 7734053

Claim:
An encoding apparatus that compresses a stereo signal using a sum signal and a difference signal of a left component signal and a right component signal of the stereo signal, comprising: a transforming unit configured to transform a left spectrum signal and a right spectrum signal to produce a sum signal and a difference signal; a comparing unit configured to compare a value indicative of an output of the difference signal with a threshold for each frequency band; a correcting unit configured to correct the value to zero when the value is lower than the threshold; a calculating unit configured to calculate complexity of the sum signal and complexity of the difference signal; a setting unit configured to set, based on the complexity, an allocation rate of bits to be allocated in quantizing the sum signal and the difference signal; and a quantizing unit configured to quantize the sum signal and the difference signal based on the allocation rate, wherein the calculating unit includes: an error and power calculating unit responsive to the transforming unit and the correcting unit for producing admissible error signals and electric power signals, a perceptual entropy value calculating unit responsive to the error and power calculating unit for calculating first and second values indicative of perceptual entropy of the sum signal and the difference signal, and the complexity is calculated based on the first and second calculated values.