Signal Processing Method and Device

• US 20200135218A1
• Filed: 12/23/2019
• Published: 04/30/2020
• Est. Priority Date: 04/29/2014
• Status: Active Grant

• Current Assignee: Huawei Technologies Co., Ltd. (Huawei Investment & Holding Co., Ltd.)
• Original Assignee: Huawei Technologies Co., Ltd. (Huawei Investment & Holding Co., Ltd.)
• Inventors: Wang, Bin, Miao, Lei, Liu, Zexin
• Granted Patent: US 11,081,121 B2
• Time in Patent Office: Days
• CPC Class Codes: G10L 19/002 Dynamic bit allocation for perceptual audio coders G10L19/032
• 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

Abstract

A signal processing method and device includes obtaining spectral coefficients of a current frame of an audio signal, in which N sub-bands of the current frame comprises at least one of the spectral coefficients. A total energy of M successive sub-bands of the N sub-bands, a total energy of K successive sub-bands of the N sub-bands, and an energy of a first sub-band are obtained to determine whether to modify original envelope values of the M sub-bands. When the original envelope values of the M sub-bands are modified, encoding bits are allocated to each of the N sub-bands according to the modified envelope values of the M sub-bands.

Claims

1. An audio signal processing method implemented by an audio signal encoder, the audio signal processing method comprising:

obtaining an analog audio signal;

converting the analog audio signal to a digital time domain audio signal;

transforming the digital time domain audio signal to a frequency domain audio signal, wherein a current frame of the frequency domain audio signal comprises a plurality of spectral coefficients, wherein each of N sub-bands of the current frame comprises at least one of the spectral coefficients, and wherein N is a positive integer greater than 1;

obtaining a total energy of M successive sub-bands of the N sub-bands;

determining a largest sub-band energy among the M successive sub-bands;

obtaining a total energy of K successive sub-bands of the N sub-bands, wherein the M successive sub-bands and the K successive sub-bands are separate, wherein M and K are positive integers, and wherein N=M+K;

modifying original envelope values of the M successive sub-bands individually to obtain modified envelope values of the M successive sub-bands when the total energy of the M successive sub-bands is greater than the total energy of the K successive sub-bands multiplied by a first factor, when the total energy of the M successive sub-bands is less than the total energy of the K successive sub-bands multiplied by a second factor and when the energy of a first sub-band of the N sub-bands multiplied by a third factor and further multiplied by M is greater than the total energy of the M successive sub-bands, wherein the first factor is less than the second factor, wherein the modified envelope values of the M successive sub-bands is a determining factor for allocating encoding bits to the N sub-bands, and wherein at least one sub-band of the N sub-bands has at least one encoding bit allocated;

quantizing spectral coefficients of each sub-band that has at least one encoding bit allocated using the at least one encoding bit;

writing the spectral coefficients of each sub-band that has the at least one encoding bit into a bitstream in response to quantizing the spectral coefficients of each sub-band that has at least one encoding bit; and

sending the bitstream via a network interface.

2. The method according to claim 1, wherein the first factor is ⅙

.

3. The method according to claim 2, wherein the third factor is 0.575 in response to an encoded bandwidth of the frequency domain audio signal being between 0 to 4 kilohertz (kHz).

4. The method according to claim 2, wherein the third factor is 0.5 in response to an encoded bandwidth of the frequency domain audio signal being between 0 to 8 kilohertz (kHz).

5. The method according to claim 1, wherein the second factor is ⅔

.

6. The method according to claim 1, wherein modifying the original envelope values of the M successive sub-bands individually to obtain the modified envelope values of the M successive sub-bands comprises:

determining a modification factor for each of the M successive sub-bands based on the total energy of the M successive sub-bands and the energy of the first sub-band; and

modifying the original envelope values of each of the M successive sub-bands using the modification factor to obtain the modified envelope values of the M sub-bands.

7. The method according to claim 6, wherein the modification factor is determined according to the following equation:

8. The method according to claim 1, wherein the energy of the first sub-band is determined according to the following equation:

9. An audio signal encoder, comprising:

a microphone configured to obtain an analog audio signal;

an analog to digital (A/D) converter coupled to the microphone and configured to convert the analog audio signal to a digital time domain audio signal;

a digital signal processor coupled to the A/D converter configured to;

transform the digital time domain audio signal to a frequency domain audio signal, wherein a current frame of the frequency domain audio signal comprises a plurality of spectral coefficients, wherein each of N sub-bands of the current frame comprises at least one of the spectral coefficients, and wherein N is a positive integer greater than 1;

obtain a total energy of M successive sub-bands of the N sub-bands;

determine a largest sub-band energy among the M successive sub-bands;

obtain a total energy of K successive sub-bands of the N sub-bands, wherein the M successive sub-bands and the K successive sub-bands are separate and distinct, wherein M and K are positive integers, and wherein N=M+K;

modify original envelope values of the M successive sub-bands individually to obtain modified envelope values of the M successive sub-bands when the total energy of the M successive sub-bands is greater than the total energy of the K successive sub-bands multiplied by a first factor, when the total energy of the M successive sub-bands is less than the total energy of the K successive sub-bands multiplied by a second factor, and when the energy of a first sub-band of the N sub-bands multiplied by a third factor and further multiplied by M is greater than the total energy of the M successive sub-bands, wherein the first factor is less than the second factor, wherein the modified envelope values of the M successive sub-bands is a determining factor for allocating encoding bits to the N sub-bands, and wherein at least one sub-band of the N sub-bands has at least one encoding bit allocated;

quantize spectral coefficients of each sub-band that has at least one encoding bit allocated using the at least one encoding bit;

write the spectral coefficients of each sub-band that has the at least one encoding bit into a bitstream in response to quantizing the spectral coefficients of each sub-band that has at least one encoding bit; and

a network interface configured to send the bitstream via a network interface.

10. The device according to claim 9, wherein the first factor is ⅙

.

11. The device according to claim 9, wherein the second factor is ⅔

.

12. The device according to claim 9, wherein the third factor is 0.575 in response to an encoded bandwidth of the frequency domain audio signal being between 0 to 4 Kilohertz (KHz).

13. The device according to claim 9, wherein the third factor is 0.5 in response to an encoded bandwidth of the frequency domain audio signal being between 0 to 8 Kilohertz (KHz).

14. The device according to claim 9, wherein the digital signal processor is further configured to:

determine a modification factor for each of the M successive sub-bands based on the total energy of the M successive sub-bands and the energy of the first sub-band; and

modify the original envelope values of each of the M successive sub-bands using the modification factor to obtain the modified envelope values of the M sub-bands.

15. The device according to claim 14, wherein the digital signal processor is further configured to determine the modification factor according to the following equation:

16. The device according to claim 9, wherein the digital signal processor is further configured to determine the energy of the first sub-band according to the following equation:

17. A non-transitory computer readable storage medium, embodying computer program code, which, when executed by a computer processor, causes the computer processor to be configured to:

transform a digital time domain audio signal obtained by an analog to digital converter to a frequency domain audio signal, wherein a current frame of the frequency domain audio signal comprises a plurality of spectral coefficients, wherein each of N sub-bands of the current frame comprises at least one of the spectral coefficients, and wherein N is a positive integer greater than 1;

obtain a total energy of M successive sub-bands of the N sub-bands;

determine a largest sub-band energy among the M successive sub-bands;

obtain a total energy of K successive sub-bands of the N sub-bands, wherein the M successive sub-bands and the K successive sub-bands are separate and distinct, wherein M and K are positive integers, and wherein N=M+K;

modify original envelope values of the M successive sub-bands individually to obtain modified envelope values of the M successive sub-bands when the total energy of the M successive sub-bands is greater than the total energy of the K successive sub-bands multiplied by a first factor, when the total energy of the M successive sub-bands is less than the total energy of the K successive sub-bands multiplied by a second factor, and when the energy of a first sub-band of the N sub-bands multiplied by a third factor and further multiplied by M is greater than the total energy of the M successive sub-bands, wherein the first factor is less than the second factor, wherein the modified envelope values of the M successive sub-bands is a determining factor for allocating encoding bits to the N sub-bands, and wherein at least one sub-band of the N sub-bands has at least one encoding bit allocated;

quantize spectral coefficients of each sub-band that has at least one encoding bit allocated using the at least one encoding bit;

write the spectral coefficients of each sub-band that has the at least one encoding bit into a bitstream in response to quantizing the spectral coefficients of each sub-band that has at least one encoding bit; and

send the bitstream via a network interface.

18. The non-transitory computer readable storage medium according to claim 17, wherein the first factor is ⅙

, wherein the second factor is ⅔

, and wherein the third factor is 0.575 in response to an encoded bandwidth of the analog audio signal being between 0 to 4 Kilohertz (KHz).

19. The non-transitory computer readable storage medium according to claim 17, wherein the first factor is ⅙

, wherein the second factor is ⅔

, and wherein the third factor is 0.5 in response to an encoded bandwidth of the audio signal being between 0 to 8 Kilohertz (KHz).

20. The non-transitory computer readable storage medium according to claim 17, wherein the computer program code further causes the computer processor to be configured to:

determine a modification factor for each of the M successive sub-bands based on the total energy of the M successive sub-bands and the energy of the first sub-band; and

modify the original envelope values of each of the M successive sub-bands using the modification factor to obtain the modified envelope values of the M sub-bands.