Method and apparatus for encoding multi-channel audio signal and method and apparatus for decoding multi-channel audio signal

An apparatus for encoding multi-channel audio signals, the apparatus comprising:

• a multi-channel encoding unit which performs parametric encoding on input multi-channel audio signals to generate a downmixed audio signal and first additional information used to restore the multi-channel audio signals from the downmixed audio signal;
• a residual signal generating unit which restores the multi-channel audio signals from the downmixed audio signal using the downmixed audio signal and the first additional information, and which generates a residual signal corresponding to a difference value between each of the input multi-channel audio signals and the corresponding restored multi-channel audio signal;
• a residual signal encoding unit which generates second additional information representing characteristics of the residual signal;
• and
• a multiplexing unit which multiplexes the downmixed audio signal, the first additional information, and the second additional information,
• wherein the second additional information comprises an interchannel correlation (ICC) parameter representing a correlation between the input multi-channel audio signals of two different channels, and
• wherein the residual signal is not multiplexed with the downmixed audio signal, the first additional information, and the second additional information.

A method of decoding multi-channel audio signals, the method comprising:

• extracting, from encoded audio data, a downmixed audio signal, first additional information used to restore multi-channel audio signals from the downmixed audio signal, and second additional information representing characteristics of a residual signal, which corresponds to a difference value between each of input multi-channel audio signals before encoding to the downmixed audio signal and the corresponding restored multi-channel audio signal after the encoding;
• restoring a first multi-channel audio signal by using the downmixed audio signal and the first additional information;
• generating a second multi-channel audio signal having a predetermined phase difference with respect to the restored first multi-channel audio signal by using the downmixed audio signal and the first additional information;
• and
• generating a final restored audio signal by combining the restored first multi-channel audio signal and the generated second multi-channel audio signal by using the second additional information.

An apparatus for decoding multi-channel audio signals, the apparatus comprising:

• a demultiplxing unit which extracts, from encoded audio data, a downmixed audio signal, first additional information used to restore multi-channel audio signals from the downmixed audio signal, and second additional information representing characteristics of a residual signal, which corresponds to a difference value between each of input multi-channel audio signals before encoding to the downmixed audio signal and the corresponding restored multi-channel audio signal after the encoding;
• a multi-channel decoding unit which restores a first multi-channel audio signal by using the downmixed audio signal and the first additional information;
• a phase shifting unit which generates a second multi-channel audio signal having a predetermined phase difference with respect to the restored first multi-channel audio signal by using the downmixed audio signal and the first additional information;
• and
• a combining unit which combines the restored first multi-channel audio signal and the generated second multi-channel audio signal by using the second additional information to generate a final restored audio signal.

A method of encoding multi-channel audio signals, the method comprising:

• performing parametric encoding on input multi-channel audio signals to generate a downmixed audio signal;
• restoring the multi-channel audio signals from the downmixed audio signal;
• generating a residual signal corresponding to a difference value between each of the input multi-channel audio signals and the corresponding restored multi-channel audio signal;
• generating additional information representing characteristics of the residual signal;
• and
• multiplexing the downmixed audio signal and the additional information,
• wherein the additional information comprises an interchannel correlation (ICC) parameter representing a correlation between the input multi-channel audio signals of two different channels, and
• wherein the residual signal is not multiplexed with the downmixed audio signal and the additional information.

A method of generating final restored multi-channel audio signals from a downmixed audio signal, the method comprising:

• extracting, from encoded audio data, the downmixed audio signal and additional information representing characteristics of a residual signal, which corresponds to a difference value between each of input multi-channel audio signals before encoding to the downmixed audio signal and the corresponding restored multi-channel audio signal after the encoding;
• restoring a first multi-channel audio signals from the downmixed audio signal;
• generating a second multi-channel audio signal having a predetermined phase difference with respect to the first multi-channel audio signal;
• and
• generating the final restored multi-channel audio signals by combining the first multi-channel audio signal and the second multi-channel audio signal by using the additional information.