Audio encoding method and apparatus

• US 10,347,267 B2
• Filed: 08/21/2017
• Issued: 07/09/2019
• Est. Priority Date: 06/24/2014
• Status: Active Grant

• Current Assignee: Top Quality Telephony LLC
• Original Assignee: Huawei Technologies Co., Ltd. (Huawei Investment & Holding Co., Ltd.)
• Inventors: Wang, Zhe
• Primary Examiner(s): He, Jialong
• Application Number:
  US15/682,097
• Publication Number:
  US 20170345436A1
• Time in Patent Office: 687 Days
• CPC Class Codes: G10L 19/02 using spectral analysis, e.g. transform vocoders or subband vocoders
• CPC Class Codes: G10L 19/0204 using subband decomposition
• CPC Class Codes: G10L 19/035 Scalar quantisation
• CPC Class Codes: G10L 19/04 using predictive techniques
• CPC Class Codes: G10L 19/06 Determination or coding of the spectral characteristics, e.g. of the short-term prediction coefficients
• CPC Class Codes: G10L 19/20 using sound class specific coding, hybrid encoders or object based coding
• CPC Class Codes: G10L 19/22 Mode decision, i.e. based on audio signal content versus external parameters
• CPC Class Codes: G10L 25/03 characterised by the type of extracted parameters

Abstract

An audio encoding method and an apparatus are provided. The method includes: determining sparseness of distribution, on spectrums, of energy of N input audio frames (101), where the N audio frames include a current audio frame, and N is a positive integer; and determining, according to the sparseness of distribution, on the spectrums, of the energy of the N audio frames, whether to use a first encoding method or a second encoding method to encode the current audio frame (102), where the first encoding method is an encoding method that is based on time-frequency transform and transform coefficient quantization and that is not based on linear prediction, and the second encoding method is a linear-predication-based encoding method. The method can reduce encoding complexity and ensure that encoding is of relatively high accuracy.

Claims

1. An audio encoding method, comprising:

dividing an energy spectrum of each of N audio frames into P fast Fourier transform (FFT) energy spectrum coefficients, wherein P and N are positive integers, and the N audio frames comprise a current audio frame;

determining a general sparseness parameter according to energy of the P FFT energy spectrum coefficients of each of the N audio frames by determining an average value of minimum bandwidths of distribution on spectrums of a first preset proportion of energy of the N audio frames according to the energy of the P FFT energy spectrum coefficients of each of the N audio frames, wherein the general sparseness parameter comprises a first minimum bandwidth, wherein the average value of the minimum bandwidths of the distribution on spectrums of the first preset proportion of the energy of the N audio frames is used as the first minimum bandwidth, and wherein the general sparseness parameter indicates sparseness of distribution in energy spectrums of the N audio frames; and

determining, based on the sparseness of distribution, whether to use a first encoding method or a second encoding method to encode the current audio frame, wherein the first encoding method is based on time-frequency transform and transform coefficient quantization, and the second encoding method is a linear-predication-based encoding method, and

wherein the first encoding method is determined to be used to encode the current audio frame based on a condition that the first minimum bandwidth is less than a first preset value, or the second encoding method is determined to be used to encode the current audio frame based on a condition that the first minimum bandwidth is greater than the first preset value.

2. The method according to claim 1, wherein the determining the average value of minimum bandwidths of the first preset proportion of the energy of the N audio frames comprises:

sorting the energy of the P FFT energy spectrum coefficients of each audio frame in descending order;

comparing energy obtained after each time of accumulation with the total energy of the audio frame, and if a proportion is greater than the first preset proportion, ending the accumulation process, where a quantity of times of accumulation is the minimum bandwidth; and

determining the average value of minimum bandwidths according to the minimum bandwidth of distribution, on the spectrum, of the energy that accounts for not less than the first preset proportion of each of the N audio frames.

3. The method according to claim 1, wherein the general sparseness parameter comprises a first energy proportion, and wherein

the determining the general sparseness parameter comprises:

selecting P₁ FFT energy spectrum coefficients from the P FFT energy spectrum coefficients of each of the N audio frames; and

determining the first energy proportion according to energy of the P₁ FFT energy spectrum coefficients of each of the N audio frames and total energy of the N audio frames, wherein P₁ is a positive integer less than P,

wherein the first encoding method is determined to be used to encode the current audio frame based on a condition that the first energy proportion is greater than a second preset value, or the second encoding method is determined to be used to encode the current audio frame based on a condition that the first energy proportion is less than the second preset value.

4. The method according to claim 3, wherein energy of any one of the P₁ FFT energy spectrum coefficients is greater than energy of any one of FFT energy spectrum coefficients in the P FFT energy spectrum coefficients other than the P₁ FFT energy spectrum coefficients.

5. The method according to claim 1, wherein the general sparseness parameter comprises a second minimum bandwidth and a third minimum bandwidth, and wherein

the determining the general sparseness parameter comprises:

determining an average value of minimum bandwidths of distribution, on the spectrums, of a second preset proportion of the energy of the N audio frames according to the energy of the P FFT energy spectrum coefficients of each of the N audio frames; and

determining an average value of minimum bandwidths of distribution, on the spectrums, of a third preset proportion of the energy of the N audio frames according to the energy of the P FFT energy spectrum coefficients of each of the N audio frames,

wherein the average value of the minimum bandwidths of the second preset proportion of the energy of the N audio frames is used as the second minimum bandwidth,

wherein the average value of the minimum bandwidths of the third preset proportion of the energy of the N audio frames is used as the third minimum bandwidth,

wherein the second preset proportion is less than the third preset proportion,

wherein the first encoding method is determined to be used to encode the current audio frame based on a condition that the second minimum bandwidth is less than a third preset value and the third minimum bandwidth is less than a fourth preset value, or

the first encoding method is determined to be used to encode the current audio frame based on a condition that the third minimum bandwidth is less than a fifth preset value, or

the second encoding method is determined to be used to encode the current audio frame based on a condition that the third minimum bandwidth is greater than a sixth preset value, and wherein

the fourth preset value is greater than or equal to the third preset value, the fifth preset value is less than the fourth preset value, and the sixth preset value is greater than the fourth preset value.

6. The method according to claim 5, wherein the determining the average value of minimum bandwidths of the second preset proportion of the energy of the N audio frames and the determining the average value of minimum bandwidths of the third preset proportion of the energy of the N audio frames comprises:

sorting the energy of the P FFT energy spectrum coefficients of each audio frame in descending order;

determining, according to the sorted energy of the P FFT energy spectrum coefficients of each audio frame, a minimum bandwidth of distribution, on the spectrum, of energy that accounts for not less than the second preset proportion of each of the N audio frames;

determining, according to the minimum bandwidth of distribution, on the spectrum, of the energy that accounts for not less than the second preset proportion of each of the N audio frames, an average value of minimum bandwidths of distribution, on the spectrums, of energy that accounts for not less than the second preset proportion of the N audio frames;

determining, according to the energy, sorted in descending order, of the P FFT energy spectrum coefficients of each of the N audio frames, a minimum bandwidth of distribution, on the spectrum, of energy that accounts for not less than the third preset proportion of each of the N audio frames; and

determining, according to the minimum bandwidth of distribution, on the spectrum, of the energy that accounts for not less than the third preset proportion of each of the N audio frames, an average value of minimum bandwidths of distribution, on the spectrums, of energy that accounts for not less than the third preset proportion of the N audio frames.

7. The method according to claim 1, wherein the general sparseness parameter comprises a second energy proportion and a third energy proportion, and wherein

the determining the general sparseness parameter comprises:

determining the second energy proportion according to energy of P₂ FFT energy spectrum coefficients of each of the N audio frames and total energy of the N audio frames;

determining the third energy proportion according to energy of P₃ FFT energy spectrum coefficients of each of the N audio frames and the total energy of the N audio frames, wherein P₂ and P₃ are positive integers less than P, and P₂ is less than P₃,

and wherein the first encoding method is determined to be used to encode the current audio frame based on a condition that the second energy proportion is greater than a seventh preset value and the third energy proportion is greater than an eighth preset value, or

the first encoding method is determined to be used to encode the current audio frame based on a condition that the second energy proportion is greater than a ninth preset value, or

the second encoding method is determined to be used to encode the current audio frame based on a condition that the third energy proportion is less than a tenth preset value.

8. The method according to claim 7, wherein the P₂ FFT energy spectrum coefficients have maximum energy among possible selections of P₂ FFT energy spectrum coefficients from the P FFT energy spectrum coefficients, and wherein

the P₃ FFT energy spectrum coefficients have maximum energy among possible selections of P₃ FFT energy spectrum coefficients from the P FFT energy spectrum coefficients.

9. The method according to claim 1, wherein the N is 1.

10. The method according to claim 1, wherein the first encoding method is not based on linear prediction.

20. The audio encoder according to claim 10, wherein the first encoding method is not based on linear prediction.

11. An audio encoder, comprising:

a memory comprising instructions; and

one or more processors in communication with the memory, wherein the one or more processors execute the instructions to;

divide an energy spectrum of each of N audio frames into P fast Fourier transform (FFT) energy spectrum coefficients, wherein P and N are positive integers, and the N audio frames comprise a current audio frame;

determine a general sparseness parameter according to energy of the P FFT energy spectrum coefficients of each of the N audio frames by determining an average value of minimum bandwidths of distribution on the spectrums of a first preset proportion energy of the N audio frames according to the energy of the P FFT energy spectrum coefficients of each of the N audio frames, wherein the general sparseness parameter comprises a first minimum bandwidth, wherein the average value of the minimum bandwidths of the distribution on the spectrums of the first preset proportion of the energy of the N audio frames is used as first minimum bandwidth, and wherein the general sparseness parameter indicates sparseness of distribution in energy spectrums of the N audio frames; and

determine, based on the sparseness of distribution, whether to use a first encoding method or a second encoding method to encode the current audio frame, wherein the first encoding method is based on time-frequency transform and transform coefficient quantization, and the second encoding method is a linear-predication-based encoding method,

and wherein the first encoding method is determined to be used to encode the current audio frame based on a condition that the first minimum bandwidth is less than a first preset value, or the second encoding method is determined to be used to encode the current audio frame based on a condition that the first minimum bandwidth is greater than the first preset value.

12. The audio encoder according to claim 11, wherein, to determine the average value of minimum bandwidths, the one or more processors execute the instructions to:

sort the energy of the P FFT energy spectrum coefficients of each audio frame in descending order;

compare energy obtained after each time of accumulation with the total energy of the audio frame, and if a proportion is greater than the first preset proportion, end the accumulation process, where a quantity of times of accumulation is the minimum bandwidth; and

determine the average value of minimum bandwidths according to the minimum bandwidth of distribution, on the spectrum, of the energy that accounts for not less than the first preset proportion of each of the N audio frames.

13. The audio encoder according to claim 11, wherein the general sparseness parameter comprises a first energy proportion, and wherein,

to determine the general sparseness parameter, the one or more processors execute the instructions to:

select P₁ FFT energy spectrum coefficients from the P FFT energy spectrum coefficients of each of the N audio frames, and determine the first energy proportion according to energy of the P₁ FFT energy spectrum coefficients of each of the N audio frames and total energy of the N audio frames, wherein P₁ is a positive integer less than P, and

wherein the first encoding method is determined to be used to encode the current audio frame based on a condition that the first energy proportion is greater than a second preset value, or the second encoding method is determined to be used to encode the current audio frame based on a condition that the first energy proportion is less than the second preset value.

14. The audio encoder according to claim 13, wherein energy of any one of the P₁ FFT energy spectrum coefficients is greater than energy of any one of FFT energy spectrum coefficients in the P FFT energy spectrum coefficients other than the P₁ FFT energy spectrum coefficients.

15. The audio encoder according to claim 11, wherein the general sparseness parameter comprises a second minimum bandwidth and a third minimum bandwidth, and wherein,

to determine the general sparseness parameter, the one or more processors execute the instructions to:

determine an average value of minimum bandwidths of distribution, on the spectrums, of a second preset proportion of the energy of the N audio frames according to the energy of the P FFT energy spectrum coefficients of each of the N audio frames and determine an average value of minimum bandwidths of distribution, on the spectrums, of third preset proportion energy of the N audio frames according to the energy of the P FFT energy spectrum coefficients of each of the N audio frames, wherein the average value of the minimum bandwidths of the second preset proportion of the energy of the N audio frames is used as the second minimum bandwidth, the average value of the minimum bandwidths of the third preset proportion of the energy of the N audio frames is used as the third minimum bandwidth, and the second preset proportion is less than the third preset proportion,

wherein the first encoding method is determined to be used to encode the current audio frame based on a condition that the second minimum bandwidth is less than a third preset value and the third minimum bandwidth is less than a fourth preset value, or the first encoding method is determined to be used to encode the current audio frame based on a condition that the third minimum bandwidth is less than a fifth preset value, or the second encoding method is determined to be used to encode the current audio frame based on a condition that the third minimum bandwidth is greater than a sixth preset value, and

wherein the fourth preset value is greater than or equal to the third preset value, the fifth preset value is less than the fourth preset value, and the sixth preset value is greater than the fourth preset value.

16. The audio encoder according to claim 15, wherein, to determine the average value of minimum bandwidths, the one or more processors execute the instructions to:

sort the energy of the P FFT energy spectrum coefficients of each audio frame in descending order;

determine, according to the sorted energy of the P FFT energy spectrum coefficients of each, a minimum bandwidth of distribution, on the spectrum, of energy that accounts for not less than the second preset proportion of each of the N audio frames;

determine, according to the minimum bandwidth of distribution, on the spectrum, of the energy that accounts for not less than the second preset proportion of each of the N audio frames, an average value of minimum bandwidths of distribution, on the spectrums, of energy that accounts for not less than the second preset proportion of the N audio frames;

determine, according to the energy, sorted in descending order, of the P FFT energy spectrum coefficients of each of the N audio frames, a minimum bandwidth of distribution, on the spectrum, of energy that accounts for not less than the third preset proportion of each of the N audio frames; and

determine, according to the minimum bandwidth of distribution, on the spectrum, of the energy that accounts for not less than the third preset proportion of each of the N audio frames, an average value of minimum bandwidths of distribution, on the spectrums, of energy that accounts for not less than the third preset proportion of the N audio frames.

17. The audio encoder according to claim 11, wherein the general sparseness parameter comprises a second energy proportion and a third energy proportion, and wherein

to determine the general sparseness parameter, the one or more processors the execute instructions to:

determine the second energy proportion according to energy of P₂ FFT energy spectrum coefficients of each of the N audio frames and total energy of the respective N audio frames;

determine the third energy proportion according to energy of P₃ FFT energy spectrum coefficients of each of the N audio frames and the total energy of the N audio frames, wherein P₂ and P₃ are positive integers less than P, and P₂ is less than P₃; and

wherein the first encoding method is determined to be used to encode the current audio frame based on a condition that the second energy proportion is greater than a seventh preset value and the third energy proportion is greater than an eighth preset value, or the first encoding method is determined to be used to encode the current audio frame based on a condition that the second energy proportion is greater than a ninth preset value, or the second encoding method is determined to be used to encode the current audio frame based on a condition that the third energy proportion is less than a tenth preset value.

18. The audio encoder according to claim 17, wherein the P₂ FFT energy spectrum coefficients have maximum energy among possible selections of P₂ FFT energy spectrum coefficients from the P FFT energy spectrum coefficients, and

wherein the P₃ FFT energy spectrum coefficients have maximum energy among possible selections of P₃ FFT energy spectrum coefficients from the P FFT energy spectrum coefficients.

19. The audio encoder according to claim 11, wherein the N is 1.