Bandwidth extension with line spectral frequency parameters

1. A decoder implemented bandwidth extension method, comprising:

performing decoding operations on a bitstream encoded from an audio signal, wherein a low frequency band signal is generated via the decoding operations, and a collection of parameters is acquired via the decoding operations, and wherein the collection of parameters comprises linear prediction coefficients (LPC), a set of line spectral frequency (LSF) parameters, an adaptive codebook contribution, and an algebraic codebook contribution;

predicting a high frequency band gain according to the LPC;

selecting a signal with a frequency band from a low frequency band excitation signal as a high band excitation signal according to difference values between every two LSF parameters of the set of LSF parameters, wherein a decoding rate corresponding to the decoding operations is less than a given value, and wherein the low frequency band excitation signal is represented by a sum of the adaptive codebook contribution and the algebraic codebook contribution; and

generating a high frequency band signal from the high frequency band excitation signal and the high frequency band gain.

2. The method according to claim 1 , further comprising:

correcting the high frequency band gain according to a first correction factor, wherein the first correction factor comprises one or more of the following parameters: a voicing factor, a noise gate factor, and a spectrum tilt factor.

3. The method according to claim 2 , wherein the first correction factor is determined according to the low frequency band signal generated via the decoding operations.

4. The method according to claim 2 , further comprising:

correcting the high frequency band gain and the high frequency band excitation signal according to a second correction factor, wherein the second correction factor comprises of a classification parameter or a signal type, and the second correction factor is calculated according to the collection of parameters.

5. The method according to claim 2 , wherein the high frequency band excitation signal is based on a weighted combination of the predicted high frequency band excitation signal and a random noise signal, wherein a weight of the weighted combination is determined according to a classification parameter or a voicing factor of the low frequency band signal.

6. The method according to claim 1 , further comprising: correcting the high frequency band gain according to a pitch period acquired via the decoding operations.

7. The method according to claim 1 , wherein the generation of the high frequency band signal comprises:

correcting the high frequency band excitation signal by using the predicted high-frequency gain, and filtering the corrected high frequency band excitation signal through an LPC synthesis filter to obtain the high frequency band signal.

8. The method according to claim 1 , wherein predicting the high frequency band gain comprises:

computing an initial high frequency band gain according to the LPC; and

correcting the initial high frequency band gain according to a first correction factor to obtain the high frequency band gain, wherein the first correction factor comprises one or more of the following parameters: a voicing factor, a noise gate factor, and a spectrum tilt factor.

9. The method according to claim 1 , wherein selecting a signal with a frequency band from a low frequency band excitation signal as a high band excitation signal according to difference values between every two LSF parameters of the set of LSF parameters comprises:

calculating difference values between every two LSF parameters in the set of LSF parameters to obtain a group of difference values;

searching for a minimum difference value from the group of difference values;

determining a frequency bin corresponding to the minimum difference value; and

selecting a frequency domain excitation signal from the low-frequency excitation signal as the high frequency band excitation signal according to the frequency bin.

10. A bandwidth extension apparatus having a processor coupled to a memory storing instructions, wherein the processor executes the instructions to:

perform decoding operations on a bitstream encoded from an audio signal, wherein a low frequency band signal is generated via the decoding operations, wherein a collection of parameters is acquired via the decoding operations, and wherein the collection of parameters comprises linear prediction coefficients (LPC), a set of line spectral frequency (LSF) parameters, an adaptive codebook contribution, and an algebraic codebook contribution;

predict a high frequency band gain according to the LPC;

select a signal with a frequency band from a low frequency band excitation signal as a high band excitation signal according to difference values between every two LSF parameters of the set of LSF parameters, wherein a decoding rate corresponding to the decoding operations is less than a given value, and the low frequency band excitation signal is represented by a sum of the adaptive codebook contribution and the algebraic codebook contribution; and

generate a high frequency band signal from the high frequency band excitation signal and the high frequency band gain.

11. The apparatus according to claim 10 , wherein the processor is further configured to:

correct the high frequency band gain according to a first correction factor, wherein the first correction factor comprises one or more of the following parameters: a voicing factor, a noise gate factor, and a spectrum tilt factor.

12. The apparatus according to claim 11 , wherein the processor is configured to determine the first correction factor according to the low frequency band signal generated via the decoding operations.

13. The apparatus according to claim 11 , wherein the processor is further configured to: correct the high frequency band gain and the high frequency band excitation signal according to a second correction factor, wherein the second correction factor comprises a classification parameter or a signal type, and the second correction factor is calculated according to the collection of parameters.

14. The apparatus according to claim 11 , wherein the high frequency band excitation signal is based on a weighted combination of the predicted high frequency band excitation signal and a random noise signal, wherein a weight of the weighted combination is determined according to a classification parameter or a voicing factor of the low frequency band signal.

15. The apparatus according to claim 10 , wherein the processor is further configured to correct the high frequency band gain according to a pitch period acquired via the decoding operations.

16. The apparatus according to claim 10 , wherein the processor is configured to correct the high frequency band excitation signal by using the predicted high-frequency gain, and filtering the corrected high frequency band excitation signal through a LPC synthesis filter to obtain the high frequency band signal.

17. The apparatus according to claim 10 , wherein the processor is configured to compute an initial high frequency band gain according to the LPC, and correct the initial high frequency band gain according to a first correction factor to obtain the high frequency band gain, wherein the first correction factor comprises one or more of the following parameters: a voicing factor, a noise gate factor, and a spectrum tilt factor.

18. The apparatus according to claim 10 , wherein the processor is configured to:

calculate difference values between every two LSF parameters in the set of LSF parameters to obtain a group of difference values;

search for a minimum difference value from the group of difference values;

determine a frequency bin corresponding to the minimum difference value; and

select a frequency domain excitation signal from the low-frequency excitation signal as the high frequency band excitation signal according to the frequency bin.

19. A non-transitory computer readable media containing computer instructions that, when executed by a processor, cause the processor to perform the steps of:

performing decoding operations on a bitstream encoded from an audio signal, wherein a low frequency band signal is generated via the decoding operations, wherein a collection of parameters is acquired via the decoding operations, and wherein the collection of parameters comprises linear prediction coefficients (LPC), a set of line spectral frequency (LSF) parameters, an adaptive codebook contribution, and an algebraic codebook contribution;

predicting a high frequency band gain according to the LPC;

selecting a signal with a frequency band from a low frequency band excitation signal as a high band excitation signal according to difference values between every two LSF parameters of the set of LSF parameters, wherein a decoding rate corresponding to the decoding operations is less than a given value, and the low frequency band excitation signal is represented by a sum of the adaptive codebook contribution and the algebraic codebook contribution; and

generating a high frequency band signal from the high frequency band excitation signal and the high frequency band gain.