Apparatus and method for encoding/decoding for high frequency bandwidth extension

1. A coding method comprising:

receiving an input signal which is a time domain signal;

determining a core coding mode of a low-frequency signal of the input signal, based on characteristics of the low-frequency signal of the input signal;

extracting a linear prediction coefficient (LPC) from the low-frequency signal of the input signal, and quantizing the LPC;

performing, by using at least one processor, code excited linear prediction (CELP) coding on an LPC excitation signal of the low-frequency signal of the input signal, when the core coding mode of the low-frequency signal of the input signal is determined to be a CELP coding mode;

performing time-domain (TD) extension coding on a high-frequency signal of the input signal, when the CELP coding is performed on the LPC excitation signal;

performing audio coding on the LPC excitation signal, when the core coding mode of the low-frequency signal of the input signal is determined to be an audio coding mode;

performing frequency-domain (FD) extension coding on the high-frequency signal of the input signal, when the audio coding is performed on the LPC excitation signal;

generating a bitstream based on either (1) a result of the CELP coding and a result of TD extension coding, or (2) a result of the audio coding and a result of the FD extension coding; and

transmitting the bitstream to a decoding side for reproduction,

wherein the performing of the FD extension coding comprises:

generating a base excitation signal for a high band using the input signal;

obtaining an energy control factor of a sub-band in a frame, using the base excitation signal and the input signal;

obtaining an energy signal of the sub-band in the frame from the input signal;

controlling, by using the at least one processor, the energy signal based on the energy control factor, for the sub-band in the frame; and

quantizing the controlled energy signal, and

wherein the controlling of the energy signal is performed when the frame is a harmonic frame or a normal frame other than a transient frame.

2. The coding method of claim 1 , wherein the performing of the FD extension coding comprises performing energy quantization by sharing a same codebook at different bitrates.

3. The coding method of claim 1 , wherein the bitstream according to the result of the audio coding includes previous frame mode information.

4. A non-transitory computer readable recording medium having recorded thereon a computer program for executing the method of claim 1 .

5. The coding method of claim 1 , wherein in the obtaining of the energy signal, the energy signal is extracted corresponding to each of frequency bands.

6. The coding method of claim 1 , wherein in the quantizing of the controlled energy signal, the energy signal is vector-quantized by assigning a weight to a low-frequency band of high perceptual importance.

7. The coding method of claim 1 , wherein in the quantizing of the controlled energy signal, the energy signal is quantized by assigning a larger number of bits to a low-frequency band of high perceptual importance than to a high-frequency band.

8. The coding method of claim 1 , wherein the obtaining the energy control factor is based on a ratio between tonality of the base excitation signal and tonality of the input signal.

9. The coding method of claim 1 , wherein the quantizing the controlled energy signal comprises quantizing the controlled energy signal based on a weighted mean square error (WMSE).

10. The coding method of claim 1 , wherein the quantizing the controlled energy signal comprises quantizing the controlled energy signal based on an interpolation process.

11. The coding method of claim 1 , wherein the quantizing the controlled energy signal comprises quantizing the controlled energy signal by using a multi-stage vector quantization.

12. The coding method of claim 1 , wherein the quantizing the controlled energy signal comprises selecting a plurality of vectors from among energy vectors and quantize the selected vectors and an error obtained by interpolating the selected vectors.