Method, medium, and system encoding/decoding multi-channel signal

1. A method of generating a stereo signal from a down-mixed mono signal, the method comprising:

decoding the down-mixed mono signal included in a bitstream;

decoding parameters that represent characteristic relations between channels, included in the bitstream;

estimating a parameter representing a phase difference between one of a left signal and a right signal and the down-mixed mono signal, by using the decoded parameters; and

up-mixing the decoded down-mixed mono signal by using the decoded parameters and the estimated parameter to generate the stereo signal.

2. The method of claim 1 , wherein the decoded parameters comprise a parameter that represents an energy difference between channels of the stereo signal, and a parameter that represents a phase difference between channels of the stereo signal.

3. The method of claim 2 , wherein the estimating of the parameter comprises:

multiplying intermediate variables generated from the energy difference between channels, and by the decoded down-mixed mono signal to generate a first signal and a second signal;

generating a third signal from the energy difference between channels, and the first and second signals; and

estimating the parameter representing the phase difference between the left signal and the down-mixed mono signal, from the first, second and third signals.

4. The method of claim 2 , wherein the decoded parameters further comprise a parameter that represents a correlation between channels of the stereo signal.

5. The method of claim 1 , wherein the decoding of the down-mixed mono signal comprises:

decoding information on a domain in which the down-mixed mono signal is encoded; and

decoding the down-mixed mono signal in a time domain or a frequency domain according to the decoded information.

6. The method of claim 1 , wherein the up-mixing of the decoded down-mixed mono signal by using the decoded parameters and the estimated parameter so as to decode the stereo signal comprises interpolating a first phase of the decoded down-mixed mono signal in a current frame and a second phase of the decoded down-mixed mono signal in a previous frame to calculate the phase of the decoded down-mixed mono signal, and changing an interpolation direction according to whether the absolute value of a difference between the first phase and the second phase is greater than 180°.

7. The method of claim 1 , wherein the decoding of the parameters that represent characteristic relations between channels comprises performing context-based arithmetic decoding to decode the parameters.

8. The method of claim 1 , further comprising inversely transforming the up-mixed signal into a time domain.

9. The method of claim 1 , wherein the estimated parameter represents the phase difference between the left signal and the down-mixed mono signal.

10. A non-transitory computer readable recording medium storing a program for executing a method of decoding a multi-channel signal from a down-mixed mono signal comprising:

decoding a down-mixed mono signal representative of the multi-channel signal;

decoding parameters that represent characteristic relations between channels of the multi-channel signal;

estimating a parameter, not included in a bitstream, representing a phase difference between a left signal and the down-mixed mono signal, by using the decoded parameters; and

up-mixing the decoded down-mixed mono signal by using the decoded parameters and the estimated parameter so as to decode the multi-channel signal.

11. A method of decoding a multi-channel signal from a down-mixed mono signal, the method comprising:

decoding information on a domain in which the down-mixed mono signal representative of the multi-channel signal has been encoded;

decoding the down-mixed mono signal in a time domain or a frequency domain according to the decoded information;

decoding parameters that represent characteristic relations between channels of the multi-channel signal; and

up-mixing the decoded down-mixed mono signal by using the decoded parameters so as to decode the multi-channel signal.

12. The method of claim 11 , further comprising estimating an additional parameter by using the decoded parameters, and wherein the decoding of the multi-channel signal comprises up-mixing the decoded down-mixed mono signal by using the decoded parameters and the estimated parameter so as to decode the multi-channel signal.

13. The method of claim 12 , wherein the decoded parameters are parameters that represent an inter-channel energy difference of the multi-channel signal and an inter-channel phase difference of the multi-channel signal, and the estimated parameter is a phase parameter that represents a phase difference between the decoded down-mixed mono signal and the multi-channel signal.

14. The method of claim 13 , wherein the estimating of the additional parameter comprises:

multiplying intermediate variables generated from the inter-channel energy difference of the multi-channel signal by the decoded down-mixed mono signal to generate a first signal and a second signal;

generating a third signal from the inter-channel phase difference of the multi-channel signal and the first and second signals; and

estimating the phase parameter from the first, second and third signals.

15. A multi-channel signal decoding system comprising:

a down-mixed signal decoder to decode a down-mixed mono signal representative of a multi-channel signal;

a parameter decoder to decode parameters that represent characteristic relations between channels of the multi-channel signal;

an overall phase difference (OPD) estimator to estimate OPD, not included in a bitstream, that represents a phase difference between the decoded down-mixed mono signal and the multi-channel signal by using the decoded parameters; and

an up-mixing unit to up-mix the decoded down-mixed mono signal by using the decoded parameters and the estimated OPD.

16. The multi-channel signal decoding system of claim 15 , wherein the parameters representing characteristic relations between channels of the multi-channel signal represent an inter-channel energy difference of the multi-channel signal and an inter-channel phase difference of the multi-channel signal.