Encoder and encoding method for selecting coding mode for audio channels based on interchannel correlation

An encoder comprising:

• a calculation circuit that calculates an inter-channel correlation between a left channel and a right channel by using a left channel signal and a right channel signal that constitute a stereo signal;
• and
• an encoding circuit that encodes the left channel signal and the right channel signal by using a common coding mode when the inter-channel correlation is greater than a threshold value, and individually encodes the left channel signal and the right channel signal by using a coding mode determined for each of the left channel signal and the right channel signal when the inter-channel correlation is less than or equal to the threshold value,
• wherein the encoding circuit identifies a dominant channel and a non-dominant channel for the left channel and the right channel, calculates a weighted sum of a first parameter for determining the coding mode of the dominant channel and a second parameter for determining the coding mode of the non-dominant channel, and selects the common coding mode on the basis of a weighted parameter obtained through the weighted sum calculation.