Patent ID: 8386267

Claim:
A stereo signal coding apparatus, comprising: a sum and difference calculator that generates a monaural signal related to a sum of a first channel signal and second channel signal forming a stereo signal, and generates a side signal related to a difference between the first channel signal and the second channel signal; a mode information generator that generates mode information per layer indicating a coding mode of one of monaural coding and stereo coding; and first to N-th layer coders that perform monaural coding in an i-th layer (i=1, 2, . . . , N, where N is an integer equal to or greater than 2) using information related to the monaural signal or performs stereo coding in the i-th layer using both the information related to the monaural signal and information related to the side signal, based on the mode information, and provide i-th layer encoded information, wherein the mode information generator generates the mode information of N bits indicating the coding mode, using each of the bits, the i-th layer coder performs monaural coding in the i-th layer or performs stereo coding in the i-th layer, based on a value of an i-th bit of the mode information, and the first layer coder comprises: a first layer monaural coder that, when a value of a first bit of the mode information indicates monaural coding, performs monaural coding in a first layer using the monaural signal and outputs a coding distortion related to the monaural signal in the first layer and the side signal to the second layer coder; and a first layer stereo coder that, when the value of the first bit of the mode information indicates stereo coding, performs stereo coding in the first layer using both the monaural signal and the side signal, and outputs a coding distortion related to the monaural signal in the first layer and a coding distortion related to the side signal in the first layer to the second layer coder.