Audio coding method and apparatus

• US 9,812,143 B2
• Filed: 11/28/2016
• Issued: 11/07/2017
• Est. Priority Date: 06/27/2014
• Status: Active Grant

• Current Assignee: Top Quality Telephony LLC
• Original Assignee: Huawei Technologies Co., Ltd. (Huawei Investment & Holding Co., Ltd.)
• Inventors: Liu, Zexin, Wang, Bin, Miao, Lei
• Primary Examiner(s): Desir, Pierre-Louis
• Assistant Examiner(s): SHIN, SEONG-AH A
• Application Number:
  US15/362,443
• Publication Number:
  US 20170076732A1
• Time in Patent Office: 344 Days
• Field of Search: 704219, 704220-229, 704265, 704500
• CPC Class Codes: G10L 19/025 Detection of transients or attacks for time/frequency resolution switching
• 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 19/12 the excitation function being a code excitation, e.g. in code excited linear prediction [CELP] vocoders

Abstract

An audio coding method and apparatus, where the method includes, for each audio frame in audio, when a signal characteristic of the audio frame and a signal characteristic of a previous audio frame meet a preset modification condition, determining a first modification weight according to linear spectral frequency (LSF) differences of the audio frame and LSF differences of the previous audio frame, modifying a linear predictive parameter of the audio frame according to the determined first modification weight, and coding the audio frame according to a modified linear predictive parameter of the audio frame. According to the present disclosure, audio having a wider bandwidth can be coded while a bit rate remains unchanged or a bit rate slightly changes and a spectrum between audio frames is steadier.

Claims

1. An audio coding method comprising:

obtaining an audio signal;

performing linear prediction analysis on the audio signal to obtain a linear predictive parameter of a current frame of the audio signal;

determining a first modification weight according to linear spectral frequency (LSF) differences of the current frame of the audio signal and LSF differences of a previous frame of the current frame of the audio signal, when a signal characteristic of the current frame and a signal characteristic of the previous frame meet a preset modification condition, wherein determining the first modification weight according to LSF differences of the current frame and LSF differences of the previous frame of the current frame of the audio signal comprises determining the first modification weight according to the LSF differences of the current frame and the LSF differences of the previous frame according to

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

determining a second modification weight when the signal characteristic of the current frame and the signal characteristic of the previous frame do not meet the preset modification condition; and

modifying the linear predictive parameter of the current frame according to the determined second modification weight.

3. The method according to claim 2, wherein determining the second modification weight comprises determining a preset modification weight value as the second modification weight, and wherein the preset modification weight value is greater than 0 and is less than or equal to 1.

4. The method according to claim 1, wherein modifying the linear predictive parameter of the current frame according to the determined first modification weight comprises modifying the linear predictive parameter of the current frame according to the first modification weight according to L[i]=(1−

w[i])*L_old[i]+w[i]*L_new[i], wherein w[i] is the first modification weight, wherein L[i] is the modified linear predictive parameter of the current frame, wherein L_new[i] is the linear predictive parameter of the current frame, wherein L_old[i] is a linear predictive parameter of the previous frame, wherein a value of i ranges from 1 to M−

2, and wherein M is an order of the linear predictive parameter.

5. The method according to claim 2, wherein modifying the linear predictive parameter of the current frame according to the determined second modification weight comprises modifying the linear predictive parameter of the current frame according to the second modification weight according to L[i]=(1−

y)*L_old[i]+y*L_new[i], wherein y is the second modification weight, wherein L[i] is the modified linear predictive parameter of the current frame, wherein L_new[i] is the linear predictive parameter of the current frame, wherein L_old[i] is a linear predictive parameter of the previous frame, wherein a value of i ranges from 1 to M−

2, and wherein M is an order of the linear predictive parameter.

6. The method according to claim 1, wherein the signal characteristic of the current frame and the signal characteristic of the previous frame meet a preset modification condition when the current frame is not a transition frame, and wherein the transition frame comprises a transition from a non-fricative to a fricative or a transition from the fricative to the non-fricative.

7. The method according to claim 2, wherein the signal characteristic of the current frame and the signal characteristic of the previous frame do not meet the preset modification condition, when the current frame is a transition frame.

8. The method according to claim 6, wherein the current frame is the transition frame from the fricative to the non-fricative when a spectrum tilt frequency of the previous frame is greater than a first spectrum tilt frequency threshold and a coding type of the current frame is transient.

9. The method according to claim 6, wherein the current frame is the transition frame from the fricative to the non-fricative, when a spectrum tilt frequency of the previous frame is greater than a first spectrum tilt frequency threshold and the spectrum tilt frequency of the current frame is less than a second spectrum tilt frequency threshold.

10. The method according to claim 6, wherein the current frame is the transition frame from the non-fricative to the fricative, when a spectrum tilt frequency of the previous frame is less than a first spectrum tilt frequency threshold, and wherein a coding type of the previous frame is one of voiced, generic, transient, or audio, and wherein the spectrum tilt frequency of the current frame is greater than a second spectrum tilt frequency threshold.

11. An audio coding apparatus comprising:

a processor configured to;

obtain an audio signal;

perform linear prediction analysis on the audio signal to obtain a linear predictive parameter of a current frame of the audio signal;

determine a first modification weight according to linear spectral frequency (LSF) differences of the current frame of the audio signal and LSF differences of a previous frame of the current frame of the audio signal, when a signal characteristic of the current frame and a signal characteristic of the previous frame meet a preset modification condition, wherein the processor is further configured to determine the first modification weight according to the LSF differences of the current frame and the LSF differences of the previous frame according to

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

determine a second modification weight when the signal characteristic of the current frame and the signal characteristic of the previous frame do not meet the preset modification condition; and

modify the linear predictive parameter of the current frame according to the second modification weight.

13. The apparatus according to claim 12, wherein the processor is further configured to determine a preset modification weight value as the second modification weight, and wherein the preset modification weight value is greater than 0 and is less than or equal to 1.

14. The apparatus according to claim 11, wherein the processor is further configured to modify the linear predictive parameter of the current frame according to the first modification weight according to L[i]=(1−

w[i])*L_old[i]+w[i]*L_new[i], wherein w[i] is the first modification weight, wherein L[i] is the modified linear predictive parameter of the current frame, wherein L_new[i] is the linear predictive parameter of the current frame, wherein L_old[i] is a linear predictive parameter of the previous frame, wherein a value of i ranges from 1 to M−

2, and wherein M is an order of the linear predictive parameter.

15. The apparatus according to claim 11, wherein the processor is further configured to modify the linear predictive parameter of the current frame according to a second modification weight according to L[i]=(1−

y)*L_old[i]+y*L_new[i], wherein y is the second modification weight, wherein L[i] is the modified linear predictive parameter of the current frame, wherein L_new[i] is the linear predictive parameter of the current frame, wherein L_old[i] is the linear predictive parameter of the previous frame, wherein a value of i ranges from 1 to M−

2, and wherein M is an order of the linear predictive parameter.

16. The apparatus according to claim 11, wherein the processor is further configured to determine the first modification weight according to the LSF differences of the current frame and the LSF differences of the previous frame when the current frame is not a transition frame.

17. The apparatus according to claim 12, wherein the processor is further configured to determine the second modification weight when the current frame is a transition frame, wherein the transition frame comprises a transition from a non-fricative to a fricative, or a transition from the fricative to the non-fricative.

18. The apparatus according to claim 16, wherein the processor is further configured to:

determine the first modification weight according to the LSF differences of the current frame and the LSF differences of the previous frame when a spectrum tilt frequency of the previous frame is not greater than a first spectrum tilt frequency threshold or a coding type of the current frame is not transient; and

determine a second modification weight when the spectrum tilt frequency of the previous frame is greater than the first spectrum tilt frequency threshold and the coding type of the current frame is transient.

19. The apparatus according to claim 16, wherein the processor is further configured to:

determine the first modification weight according to the LSF differences of the current frame and the LSF differences of the previous frame when a spectrum tilt frequency of the previous frame is not greater than a first spectrum tilt frequency threshold or a spectrum tilt frequency of the current frame is not less than a second spectrum tilt frequency threshold; and

determine a second modification weight when the spectrum tilt frequency of the previous frame is greater than the first spectrum tilt frequency threshold and the spectrum tilt frequency of the current frame is less than the second spectrum tilt frequency threshold.

20. The apparatus according to claim 16, wherein the processor is further configured to:

determine the first modification weight according to the LSF differences of the current frame and the LSF differences of the previous frame when a spectrum tilt frequency of the previous frame is not less than a first spectrum tilt frequency threshold, or a coding type of the previous frame is not one of voiced, generic, transient, or audio, or a spectrum tilt of the current frame is not greater than a second spectrum tilt frequency threshold; and

determine a second modification weight when the spectrum tilt frequency of the previous frame is less than the first spectrum tilt frequency threshold, the coding type of the previous frame is one of voiced, generic, transient, or audio, and the spectrum tilt frequency of the current frame is greater than the second spectrum tilt frequency threshold.

21. An audio coding apparatus comprising:

a processor configured to;

obtain an audio signal;

perform linear prediction analysis on the audio signal to obtain a linear predictive parameter of a current frame of the audio signal;

determine a first modification weight according to linear spectral frequency (LSF) differences of the current frame of the audio signal and LSF differences of a previous frame of the current frame of the audio signal, when a signal characteristic of the current frame and a signal characteristic of the previous frame meet a preset modification condition;

modify the linear predictive parameter of the current frame according to the first modification weight;

code the current frame according to the modified linear predictive parameter;

determine the first modification weight according to the LSF differences of the current frame and the LSF differences of the previous frame when the current frame is not a transition frame;

determine the first modification weight according to the LSF differences of the current frame and the LSF differences of the previous frame when a spectrum tilt frequency of the previous frame is not greater than a first spectrum tilt frequency threshold or a spectrum tilt frequency of the current frame is not less than a second spectrum tilt frequency threshold; and

determine a second modification weight when the spectrum tilt frequency of the previous frame is greater than the first spectrum tilt frequency threshold and the spectrum tilt frequency of the current frame is less than the second spectrum tilt frequency threshold.

22. An audio coding apparatus comprising:

a processor configured to;

obtain an audio signal;

perform linear prediction analysis on the audio signal to obtain a linear predictive parameter of a current frame of the audio signal;

determine a first modification weight according to linear spectral frequency (LSF) differences of the current frame of the audio signal and LSF differences of a previous frame of the current frame of the audio signal, when a signal characteristic of the current frame and a signal characteristic of the previous frame meet a preset modification condition;

modify the linear predictive parameter of the current frame according to the first modification weight;

code the current frame according to the modified linear predictive parameter;

determine the first modification weight according to the LSF differences of the current frame and the LSF differences of the previous frame when the current frame is not a transition frame;

determine the first modification weight according to the LSF differences of the current frame and the LSF differences of the previous frame when a spectrum tilt frequency of the previous frame is not less than a first spectrum tilt frequency threshold, or a coding type of the previous frame is not one of voiced, generic, transient, or audio, or a spectrum tilt of the current frame is not greater than a second spectrum tilt frequency threshold; and

determine a second modification weight when the spectrum tilt frequency of the previous frame is less than the first spectrum tilt frequency threshold, the coding type of the previous frame is one of voiced, generic, transient, or audio, and the spectrum tilt frequency of the current frame is greater than the second spectrum tilt frequency threshold.

23. An audio coding method comprising:

obtaining an audio signal;

performing linear prediction analysis on the audio signal to obtain a linear predictive parameter of a current frame of the audio signal;

determining a first modification weight according to linear spectral frequency (LSF) differences of the current frame of the audio signal and LSF differences of a previous frame of the current frame of the audio signal, when a signal characteristic of the current frame and a signal characteristic of the previous frame meet a preset modification condition;

modifying the linear predictive parameter of the current frame according to the determined first modification weight; and

coding the current frame according to the modified linear predictive parameter,

wherein the signal characteristic of the current frame and the signal characteristic of the previous frame meet a preset modification condition when the current frame is not a transition frame, wherein the transition frame comprises a transition from a non-fricative to a fricative or a transition from the fricative to the non-fricative, and wherein the current frame is the transition frame from the fricative to the non-fricative when a spectrum tilt frequency of the previous frame is greater than a first spectrum tilt frequency threshold and a coding type of the current frame is transient.

24. An audio coding method comprising:

obtaining an audio signal;

performing linear prediction analysis on the audio signal to obtain a linear predictive parameter of a current frame of the audio signal;

determining a first modification weight according to linear spectral frequency (LSF) differences of the current frame of the audio signal and LSF differences of a previous frame of the current frame of the audio signal, when a signal characteristic of the current frame and a signal characteristic of the previous frame meet a preset modification condition;

modifying the linear predictive parameter of the current frame according to the determined first modification weight; and

coding the current frame according to the modified linear predictive parameter,

wherein the signal characteristic of the current frame and the signal characteristic of the previous frame meet a preset modification condition when the current frame is not a transition frame, wherein the transition frame comprises a transition from a non-fricative to a fricative or a transition from the fricative to the non-fricative, and wherein the current frame is the transition frame from the fricative to the non-fricative when a spectrum tilt frequency of the previous frame is greater than a first spectrum tilt frequency threshold and the spectrum tilt frequency of the current frame is less than a second spectrum tilt frequency threshold.

25. An audio coding method comprising:

obtaining an audio signal;

performing linear prediction analysis on the audio signal to obtain a linear predictive parameter of a current frame of the audio signal;

determining a first modification weight according to linear spectral frequency (LSF) differences of the current frame of the audio signal and LSF differences of a previous frame of the current frame of the audio signal, when a signal characteristic of the current frame and a signal characteristic of the previous frame meet a preset modification condition;

modifying the linear predictive parameter of the current frame according to the determined first modification weight; and

coding the current frame according to the modified linear predictive parameter,

wherein the signal characteristic of the current frame and the signal characteristic of the previous frame meet a preset modification condition when the current frame is not a transition frame, wherein the transition frame comprises a transition from a non-fricative to a fricative or a transition from the fricative to the non-fricative, wherein the current frame is the transition frame from the non-fricative to the fricative when a spectrum tilt frequency of the previous frame is less than a first spectrum tilt frequency threshold, wherein a coding type of the previous frame is one of voiced, generic, transient, or audio, and wherein the spectrum tilt frequency of the current frame is greater than a second spectrum tilt frequency threshold.