Apparatus and method for coding residual signals of audio signals into a frequency domain and apparatus and method for decoding the same

A residual signal coding method, comprising the steps of:

• a) receiving an audio signal and transforming time-domain residual signals of the received audio signal into a frequency domain to output transform coefficients;
• b) extracting linear predictive coding (LPC) coefficients from the transform coefficients;
• c) quantizing the LPC coefficients to output quantized LPC coefficients and corresponding indices;
• d) performing, using a filter made of the quantized LPC coefficients, a linear prediction (LP) analysis on the transform coefficients to output LP residual transform coefficients;
• e) splitting the LP residual transform coefficients into a predetermined number of bands to output the LP residual transform coefficients on a per-band basis;
• f) searching the LP residual transform coefficients for the respective bands to select an optimal pulse and output parameters of the optimal pulse;
• and
• g) quantizing the parameters of the optimal pulse.

A residual signal decoding apparatus comprising:

• a linear predictive coding (LPC) de-quantizer receiving quantized LPC coefficients of an audio signal and de-quantizing indices of the received quantized LPC coefficients to output restored LPC coefficients;
• a pulse de-quantizer receiving quantized pulse parameters of the audio signal and do-quantizing the received quantized Pulse parameters to output restored pulse parameters;
• a pulse generator for generating pulses from the restored pulse parameters to output restored linear prediction (LP) residual transform coefficients for respective bands;
• a band combiner for concatenating the restored LP residual transform coefficients for the respective bands with respect to all the bands to output restored LPC residual transform coefficients;
• an LP synthesis filter including a filter made of the restored LPC coefficients and performing an LP synthesis on the restored LP residual transform coefficients to output restored transform coefficients;
• and
• an inverse-transformer for inversely transforming the restored frequency-domain transform coefficients into a time domain to decode residual signals,
• wherein the decoded residual signals are inputted to an audio signal decoder to output decoded audio signals.

A residual signal decoding method, comprising the steps of:

• a) receiving quantized linear predictive coding (LPC) coefficients of an audio signal and de-quantizing the indices of the quantized linear predictive coding (LPC) coefficients to output restored LPC coefficients;
• b) receiving quantized pulse parameters of the audio signal and de-quantizing the quantized pulse parameters to output restored pulse parameters;
• c) generating pulses from the restored pulse parameters to output restored linear prediction (LP) residual transform coefficients for respective bands;
• d) adding the restored LP residual transform coefficients for the respective bands with respect to all the bands to output restored LPC residual transform coefficients;
• e) performing, using a filter made of the restored LPC coefficients, an LP synthesis on the restored LP residual transform coefficients to output restored transform coefficients;
• and
• f) inversely transforming the restored frequency-domain transform coefficients into a time domain to decode residual signals,
• g) providing the decoded residual signals to an audio signal decoder and outputting a decoded audio signal.