13. A multi-channel audio signal encoding apparatus, the apparatus comprising: a channel similarity determining unit which determines a degree of similarity between multi-channels based on semantic information for each channel; a channel signal processing unit which generates spatial parameters between similar channels determined by the channel similarity determining unit, and down-mixes audio signals of the similar channels using the similar channels so as to enhance a channel separation on a decoder; a coding unit which encodes the down-mixed audio signals of the similar channels processed by the signal processing unit by using a predetermined codec; and a bitstream formatting unit which adds the semantic information for each channel or information about the similar channels to the audio signals encoded by the coding unit, and formats the audio signals as a bitstream, wherein the channel similarity determining unit compares the degree of similarity between multi-channels with a predetermined threshold.
13. A multi-channel audio signal encoding apparatus, the apparatus comprising: a channel similarity determining unit which determines a degree of similarity between multi-channels based on semantic information for each channel; a channel signal processing unit which generates spatial parameters between similar channels determined by the channel similarity determining unit, and down-mixes audio signals of the similar channels using the similar channels so as to enhance a channel separation on a decoder; a coding unit which encodes the down-mixed audio signals of the similar channels processed by the signal processing unit by using a predetermined codec; and a bitstream formatting unit which adds the semantic information for each channel or information about the similar channels to the audio signals encoded by the coding unit, and formats the audio signals as a bitstream, wherein the channel similarity determining unit compares the degree of similarity between multi-channels with a predetermined threshold. 14. The apparatus of claim 13 , wherein the channel signal processing unit comprises: a space information generating unit which divides the similar channels into time-frequency blocks, and generates spatial parameters between the similar channels of each time-frequency block; and a down-mixing unit which down-mixes the audio signals of the similar channels.