Apparatus for encoding and decoding audio signal and method of operation thereof

An audio signal decoding method comprising:

• generating magnitudes of first linear prediction (LP) residual coefficients and phases of the first LP residual coefficients by decoding a coded audio signal;
• obtaining second LP residual coefficients by scaling the magnitudes of the LP residual coefficients based on a subband gain used for generating the coded audio signal from an original audio signal;
• generating a frequency domain signal corresponding to the original audio signal using the second LP residual coefficients and quantized LP coefficients corresponding to the original audio signal;
• and
• outputting a time domain signal corresponding to the frequency domain signal,
• wherein the subband gain comprises a second subband gain generated by changing a first subband gain based on a normalized short-time distorted block,
• wherein the first subband gain is obtained based on LP residual coefficients obtained based on a reference signal obtained from the original audio signal and a bit constraint corresponding to a subband.

An apparatus for decoding an audio signal, the apparatus comprising:

• a memory configured to store instructions;
• and
• a processor electrically connected to the memory and configured to execute the instructions,
• wherein the processor is configured to control a plurality of operations, when the instructions are executed by the processor,
• wherein the plurality of operations comprises:
• obtaining quantized linear prediction (LP) coefficients corresponding to an input audio signal;
• obtaining LP residual coefficients based on a reference signal obtained from the input audio signal;
• obtaining a first subband gain based on the LP residual coefficients and a bit constraint corresponding to a subband;
• generating a second subband gain from the first subband gain using the reference signal and the quantized LP coefficients;
• scaling the magnitudes using the second subband gain;
• and
• quantizing phases of the LP residual coefficients and the scaled magnitudes of the LP residual coefficients,
• wherein the generating of the second subband gain comprises:
• scaling the magnitudes using the first subband gain;
• generating a test signal using the magnitudes scaled using the first subband gain and the quantized LP coefficients;
• obtaining a normalized short-time distorted block corresponding to the subband using the test signal and the reference signal;
• and
• generating the second subband gain by changing the first subband gain based on the normalized short-time distorted block.