Audio encoding apparatus and method, audio decoding apparatus and method, and audio reproducing apparatus

An audio decoding method performed by a processor, comprising:

• decoding an encoded intermediate channel signal included in a bitstream, and an object sound or a background sound to be used for unmixing of the decoded intermediate channel signal;
• decoding matrix information used for the unmixing the decoded intermediate channel signal;
• unmixing the decoded intermediate channel signal using the matrix information and outputs the object sound and the background sound;
• and
• decoding metadata including control information of the object sound and outputs the decoded metadata,
• wherein a number of channels of the intermediate channel signal has the same number of channels as a number of channels of the background sound,
• wherein the encoded intermediate channel signal is obtained by encoding an intermediate channel signal using an encoder.