FRAME ERROR CONCEALMENT METHOD AND APPARATUS, AND AUDIO DECODING METHOD AND APPARATUS

1 . A frame error concealment method comprising:

predicting a parameter by performing a regression analysis on a group basis for a plurality of groups constructed from a first plurality of bands forming an error frame; and

concealing an error in the error frame by using the parameter predicted on a group basis.

2 . The frame error concealment method of claim 1 , wherein the predicted parameter is average energy of a second plurality of bands included in each group.

3 . The frame error concealment method of claim 1 , wherein the predicting of a parameter comprises:

forming the plurality of groups from the first plurality of bands;

determining signal characteristics of the error frame; and

determining the number of previous good frames (PGFs) to be used for the regression analysis according to a result of the determination and performing the regression analysis on a group basis using the determined number of PGFs.

4 . The frame error concealment method of claim 3 , wherein the determining of signal characteristics is performed using a transient flag transmitted from an encoder and comprises determining that the error frame is transient when a previous frame is transient.

5 . The frame error concealment method of claim 3 , wherein the determining of signal characteristics is performed using moving average energy obtained up to a PGF and difference energy between an energy of the PGF and the moving average energy and comprises determining that the error frame is transient according to a result of comparing the difference energy with a predetermined threshold.

6 . The frame error concealment method of claim 3 , wherein the determining of signal characteristics is performed using a transient flag transmitted from an encoder, moving average energy obtained up to a PGF, and difference energy between the error frame and the PGF.

7 . The frame error concealment method of claim 1 , wherein the concealing of an error comprises:

obtaining a gain between the parameter predicted on a group basis and a parameter of a corresponding group of a PGF; and

scaling a parameter of each band of the PGF by using the obtained gain to generate a parameter of the error frame.

8 . The frame error concealment method of claim 7 , wherein the scaling comprises, when the error frame has a burst error duration, down-scaling a portion of the burst error duration by a fixed value according to whether the error frame is transient.

9 . The frame error concealment method of claim 7 , wherein the scaling comprises, when the error frame has a burst error duration, down-scaling a portion of the burst error duration according to signal characteristics of a PGF.

10 . The frame error concealment method of claim 7 , wherein the scaling comprises, when the error frame has a burst error duration, applying a random sign to a portion of the burst error duration according to signal characteristics of a PGF.

11 . An audio encoding method comprising:

acquiring a spectral coefficient by decoding a good frame;

predicting a parameter by performing a regression analysis on a group basis for a plurality of groups formed from a first plurality of bands forming an error frame and acquiring a spectral coefficient of the error frame by using the parameter predicted on a group basis; and

transforming a decoded spectral coefficient of the good frame or the error frame into a time domain and reconstructing a signal in the time domain by performing an overlap-and-add process.

12 . The audio encoding method of claim 11 , wherein, in the overlap-and-add process, when a current frame is a good frame, a previous frame is an error frame, and a decoding mode of a latest good frame is a frequency domain mode, the current frame is overlapped with a time domain signal of a next good frame (NGF).

13 . The audio encoding method of claim 11 , wherein, in the overlap-and-add process, when a current frame is a good frame, the number of continuous previous error frames is 2 or greater, a previous frame is an error frame, and an encoding mode of a latest good frame is a frequency domain mode, the current frame is overlapped with a time domain signal of a next good frame (NGF).