Frame error concealment method and apparatus, and audio decoding method and apparatus

1. A frame error concealment method comprising:

receiving a bitstream of an audio signal;

if it is determined that a current frame in the audio signal is an error frame and a number of contiguous error frames comprising the current frame is one, generating spectral coefficients of the current frame by repeating spectral coefficients of a previous frame;

if it is determined that the current frame in the audio signal is the error frame and the number of contiguous error frames comprising the current frame is equal to or greater than two,

predicting a first average norm value of the current frame, based on a regression analysis on second average norm values of a plurality of previous frames;

obtaining a gain of the current frame from the predicted first average norm value and at least one second average norm value of at least one previous frame; and

generating the spectral coefficients of the current frame from spectral coefficients of at least one previous frame, based on the obtained gain of the current frame;

inverse-transforming the generated spectral coefficients of the current frame; and

reconstructing the audio signal based on the inverse-transformed spectral coefficients of the current frame,

wherein if it is determined that the current frame is the error frame, a first previous frame preceding the current frame is not the error frame, a second previous frame preceding the first previous frame is the error frame and the number of contiguous error frames is one, the regression analysis is applied for the current frame.

2. The frame error concealment method of claim 1 , wherein the predicting the first average norm value further comprises:

determining signal characteristics of the current frame; and

determining how many of previous frames with no error are to be used for the regression analysis in response to the determined signal characteristics.

3. The frame error concealment method of claim 2 , wherein the determining the signal characteristics is performed based on at least a transient flag transmitted from an encoder.

4. The frame error concealment method of claim 2 , wherein the determining the signal characteristics is performed based on a frame type and an energy difference between a current frame energy and a moving average energy.

5. The frame error concealment method of claim 1 , further comprising if it is determined that the current frame in the audio signal is the error frame and the number of contiguous error frames comprising the current frame is the same or greater than two, determining a location to which adaptive muting is applied among the contiguous error frames, based on signal characteristics.

6. The frame error concealment method of claim 5 , wherein if the location to which the adaptive muting is applied corresponds to the current frame, the current frame is muted to a fixed value.

7. The frame error concealment method of claim 1 , wherein the predicting comprises performing a linear regression analysis.