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

1. An apparatus for coding an input signal comprising:

at least one of processor configured to:

classify a coding mode of a low-frequency signal of the input signal based on characteristics of the low-frequency signal of the input signal;

when the coding mode is classified as a speech coding mode, perform code excited linear prediction (CELP) coding on a linear prediction coefficient (LPC) excitation signal of the low-frequency signal of the input signal;

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

when the coding mode is classified as an audio coding mode, perform audio coding on the LPC excitation signal of the low-frequency signal of the input signal; and

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

wherein said at least one of processor is further configured to:

when the frequency-domain extension coding is performed, generate a base excitation signal for a high band using an input spectrum;

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

generate an energy signal based on the input spectrum and the energy control factor, for the sub-band in the frame; and

quantize the generated energy signal.

2. The apparatus of claim 1 , wherein the at least one of processor is further configured to, when the frequency-domain extension coding is performed, perform energy quantization by sharing a same codebook at different bitrates.

3. The apparatus of claim 1 , wherein the at least one of processor is further configured to vector-quantize the energy signal by assigning a weight to a low-frequency band of high perceptual importance.

4. The apparatus of claim 1 , wherein the at least one of processor is further configured to quantize the energy signal by assigning a larger number of bits to a low-frequency band of high perceptual importance than to a high-frequency band.

5. The apparatus of claim 1 , wherein the at least one of processor is further configured to obtain the energy control factor based on a ratio between tonality of the base excitation signal and tonality of the input spectrum.

6. The apparatus of claim 1 , wherein the at least one of processor is further configured to quantize the energy signal based on a weighted mean square error (WMSE).

7. The apparatus of claim 1 , wherein the at least one of processor is further configured to quantize the energy signal based on an interpolation process.

8. The apparatus of claim 1 , wherein the at least one of processor is further configured to quantize the energy signal by using a multi-stage vector quantization.

9. The apparatus of claim 1 , wherein the at least one of processor is further configured to select a plurality of vectors from among energy vectors and quantize the selected vectors and an error obtained by interpolating the selected vectors.

10. A method for coding an input signal, wherein the method comprising:

classifying a coding mode of a low-frequency signal of the input signal based on characteristics of the low-frequency signal of the input signal;

when the coding mode is classified as a speech coding mode, performing code excited linear prediction (CELP) coding on a linear prediction coefficient (LPC) excitation signal of the low-frequency signal of the input signal;

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

when the coding mode is classified as an audio coding mode, performing audio coding on the LPC excitation signal of the low-frequency signal of the input signal; and

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

wherein the performing of the FD extension coding comprises:

generating a base excitation signal for a high band using an input spectrum;

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

generating an energy signal based on the input spectrum and the energy control factor, for the sub-band in the frame; and

quantizing the generated energy signal.

11. The method of claim 10 , wherein the performing of the FD extension coding comprises performing energy quantization by sharing a same codebook at different bitrates.

12. The method of claim 10 , wherein the quantizing of the generated energy signal comprises vector-quantizing the energy signal by assigning a weight to a low-frequency band of high perceptual importance.

13. The method of claim 10 , wherein the quantizing of the generated energy signal comprises quantizing the energy signal by assigning a larger number of bits to a low-frequency band of high perceptual importance than to a high-frequency band.

14. The method of claim 10 , wherein the obtaining of the energy control factor comprises obtaining the energy control factor based on a ratio between tonality of the base excitation signal and tonality of the input spectrum.

15. The method of claim 10 , wherein the quantizing of the generated energy signal comprises quantizing the energy signal based on a weighted mean square error (WMSE).

16. The method of claim 10 , wherein the quantizing of the generated energy signal comprises quantizing the energy signal based on an interpolation process.

17. The method of claim 10 , wherein the quantizing of the generated energy signal comprises quantizing the energy signal by using a multi-stage vector quantization.

18. The method of claim 10 , wherein the quantizing of the generated energy signal comprises selecting a plurality of vectors from among energy vectors and quantizing the selected vectors and an error obtained by interpolating the selected vectors.