Apparatus and method for bandwidth extension for multi-channel audio

1. A multi-channel audio signal encoding apparatus, the apparatus comprising:

a downmixer configured to downmix multi-channel audio input signals;

a channel decorrelator configured to expand the number of channels of the downmixed signals, thereby providing expanded channel signals;

a parameter estimator configured to select a signal from among the downmixed signals and expanded channel signals and to extract a parameter indicating a characteristic relation between the selected signal and the multi-channel audio input signals; and

a bitmuxer configured to encode the downmixed signals and the extracted parameter.

2. The apparatus of claim 1 , wherein the channel decorrelator expands the number of channels of the downmixed signals through linear combination or decorrelation.

3. The apparatus of claim 1 , wherein the bitmuxer encodes the extracted parameter and a signal associated with a high frequency band signal of the multi-channel audio input signals within the downmixed signals.

4. The apparatus of claim 1 , wherein the parameter estimator selects, from among the downmixed signal and the expanded channel signal, at least one signal having a maximal value when a match function is applied to the downmixed signal and the expanded channel signal with each input signal of the multi-channel audio input signal, and extracts a parameter indicating a characteristic relation between the selected signal and the multi-channel audio input signal.

5. A multi-channel audio signal decoding apparatus, the apparatus comprising:

a bitdemuxer configured to generate, from an input bitstream that is obtained by encoding a multi-channel audio signal, downmixed signals by demultiplexing the input bitstream;

a parameter decoder configured to decode, from the input bit stream, a parameter to be used for restoring a channel signal included in the multi-channel audio signal;

a channel decorrelator configured to expand the number of channels of the restored downmixed signals;

a high-frequency signal synthesizer configured to select, from the downmixed signals of which the number of channels is expanded, the channel signal to be patched using the decoded parameter; and

a spatial synthesizer configured to restore the channel signal included in the multi-channel audio signal using the selected channel signal and the decoded parameter.

6. The apparatus of claim 5 , wherein the channel decorrelator expands the number of channels of the downmixed signals, through linear combination or decorrelation.

7. A multi-channel audio signal encoding method of a transmitter, the method comprising:

downmixing multi-channel audio input signals;

expanding the number of channels of the downmixed signals;

selecting a signal from among the expanded channel signals;

extracting a characteristic relation between the selected signal and the multi-channel audio input signals; and

encoding the downmixed signals and the extracted parameter.

8. The method of claim 7 , wherein the expanding comprises expanding the number of channels of the downmixed signals through linear combination or decorrelation.

9. The method of claim 7 , wherein the encoding comprises encoding the extracted parameter and a signal associated with a high frequency band signal of the multi-channel audio input signals within the downmixed signals.

10. The method of claim 7 , wherein the selecting and extracting comprises:

selecting, from among the downmixed signals and the expanded channel signals, a signal having a maximal value when a match function is applied to the downmixed signals and the expanded channel signals with each input signal of the multi-channel audio input signals; and

extracting the parameter indicating a characteristic relation between the selected signal and the multi-channel audio input signals.

11. A multi-channel audio signal decoding method of a receiver, the method comprising:

demultiplexing, from an input bitstream that is obtained by encoding a multi-channel audio signal, downmixed signals;

decoding, from the input bitstream, a parameter to be used for restoring a channel signal included in the multi-channel audio signal;

expanding the number of channels of the downmixed signals;

selecting, from the downmixed signals of which the number of channels is expanded, the channel signal to be patched using the decoded parameter; and

restoring the channel signal included in the multi-channel audio signal using the selected channel signal and the decoded parameter.

12. The method of claim 11 , wherein the expanding comprises expanding the number of channels of the downmixed signals through linear combination or decorrelation.

13. A non-transitory computer readable storage medium storing a program to implement the method of claim 7 .