System and Method for Audio Coding and Decoding

• US 20150025897A1
• Filed: 10/08/2014
• Published: 01/22/2015
• Est. Priority Date: 04/14/2010
• 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: Virette, David, Gao, Yang, Xiao, Wei
• Granted Patent: US 9,646,616 B2
• Time in Patent Office: Days
• US Class Current: 704/500
• CPC Class Codes: G10L 19/00 Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis in musical instruments G10H
• CPC Class Codes: G10L 19/26 Pre-filtering or post-filtering
• CPC Class Codes: G10L 25/18 the extracted parameters being spectral information of each sub-band

Abstract

In accordance with an embodiment, a method of generating an encoded audio signal, the method includes estimating a time-frequency energy of an input audio signal from a time-frequency filter bank, computing a global variance of the time-frequency energy, determining a post-processing method according to the global variance, and transmitting an encoded representation of the input audio signal along with an indication of the determined post-processing method.

Claims

1. A method of generating an encoded audio signal, the method comprising:

estimating a time-frequency energy of an input audio signal from a time-frequency filter bank;

computing a global variance of the time-frequency energy;

determining a post-processing method according to the global variance; and

transmitting an encoded representation of the input audio signal along with an indication of the determined post-processing method.

2. The method of claim 1, wherein computing the global variance comprises estimating a variance of the time-frequency energy in a time direction.

3. The method of claim 1, wherein computing the global variance comprises estimating a variance of the time-frequency energy in a frequency direction to produce a first variance.

4. The method of claim 3, wherein computing the global variance further comprises estimating a variance of the first variance in a time direction.

5. A method for generating an encoded audio signal, the method comprising:

receiving a frame comprising a time-frequency (T/F) representation of an input audio signal, the T/F representation having time slots, each time slot having subbands;

estimating energy in subbands of the time slots;

estimating a time variance across a first plurality of time slots for each of a second plurality of subbands;

estimating a frequency variance of the time variance across the second plurality of subbands;

determining a class of audio signal by comparing the frequency variance with a threshold; and

transmitting the encoded audio signal, the encoded audio signal comprising a coded representation of the input audio signal and a control code based on the class of audio signal.

6. The method of claim 5, further comprising producing the coded representation of the input audio signal, producing the coded representation of the input audio signal comprising:

producing a low-band signal from the input audio signal;

producing low-band parameters from the low band signal;

producing the T/F representation of the input audio signal from the input audio signal; and

producing high-band parameters from the T/F representation of the input audio signal, wherein the coded representation of the input audio signal includes the low-band parameters and the high-band parameters.

7. The method of claim 5, wherein determining the class of audio signal comprises determining that the audio signal is a noise-like signal if the variance is on a first side of the threshold.

8. The method of claim 7, wherein the control code comprises at least one bit indicating whether or not the audio signal is a noise-like signal.

9. The method of claim 5, wherein comparing the frequency variance with a threshold comprises comparing the frequency variance with a plurality of thresholds to determine the class of audio signal.

10. The method of claim 9, wherein the control code comprises:

a flag indicating whether or not the class of audio signal has changed from a last frame; and

a parameter indicating the class of audio signal if the flag indicates that the class of audio signal has changed from the last frame.

11. The method of claim 5, further comprising varying the threshold with hysteresis.

12. The method of claim 5, further comprising smoothing the frequency variance before determining the class of audio signal.

13. The method of claim 5, wherein smoothing the frequency variance comprises performing a moving average of the frequency variance over a plurality of frames.

14. A system for generating an encoded audio signal the system comprising:

a detector configured to;

receive a frame comprising a time-frequency (T/F) representation of an input audio signal, the T/F representation having time slots, wherein each time slot comprises subbands,

estimate energy in subbands of the time slots,

estimate a time variance across a first plurality of time slots for each of a second plurality of subbands,

estimate a frequency variance of the time variance across the second plurality of subbands, and

determine a class of audio signal by comparing the frequency variance with a threshold; and

a transmitter configured to transmit the encoded audio signal, wherein the encoded audio signal comprises a coded representation of the input audio signal and a control code based on the class of audio signal.

15. The system of claim 14, further comprising an encoder configured to:

produce a low-band signal from the input audio signal;

produce low-band parameters from the low band signal;

produce the T/F representation of the input audio signal from the input audio signal;

produce high-band parameters from the T/F representation of the input audio signal; and

produce the coded representation of the input audio signal including the low-band parameters and the high-band parameters.

16. The system of claim 14, wherein the detector is further configured to determine the class of audio signal by determining that the audio signal is a noise-like signal if the variance is on a first side of the threshold.

17. The system of claim 16, wherein the control code comprises at least one bit indicating whether or not the audio signal is a noise-like signal.

18. The system of claim 14, wherein:

the threshold comprises a plurality of thresholds; and

the detector is configured to compare the frequency variance to the plurality of thresholds to determine the class of audio signal.

19. The system of claim 18, wherein the control code comprises:

a flag indicating whether or not the class of audio signal has changed from a last frame; and

a parameter indicating the class of audio signal if the flag indicates that the class of audio signal has changed from the last frame.

20. The system of claim 14, wherein the detector is configured to varying the threshold with hysteresis.

21. The system of claim 14, wherein the detector is further configured to smooth the frequency variance before determining the class of audio signal.

22. The system of claim 14, wherein the detector is configured to smooth the frequency variance by performing a moving average of the frequency variance over a plurality of frames.

23. A non-transitory computer readable medium with an executable program stored thereon, wherein the program instructs a microprocessor to perform the following steps:

receiving a frame comprising a time-frequency (T/F) representation of an input audio signal, the T/F representation having time slots, each time slot having subbands;

estimating energy in subbands of the time slots;

estimating a time variance across a first plurality of time slots for each of a second plurality of subbands;

estimating a frequency variance of the time variance across the second plurality of subbands;

determining a class of audio signal by comparing the frequency variance with a threshold; and

transmitting an encoded audio signal, the encoded audio signal comprising a coded representation of the input audio signal and a control code based on the class of audio signal.

24. The non-transitory computer readable medium of claim 23, wherein the program further instructs the microprocessor to produce the coded representation of the input audio signal by performing the following steps:

producing a low-band signal from the input audio signal;

producing low-band parameters from the low band signal;

producing the T/F representation of the input audio signal from the input audio signal; and

producing high-band parameters from the T/F representation of the input audio signal, wherein the coded representation of the input audio signal includes the low-band parameters and the high-band parameters.

25. The non-transitory computer readable medium of claim 23, wherein the step of determining the class of audio signal comprises determining that the audio signal is a noise-like signal if the variance is on a first side of the threshold.

26. The non-transitory computer readable medium of claim 25, wherein the control code comprises at least one bit indicating whether or not the audio signal is a noise-like signal.

27. The non-transitory computer readable medium of claim 23, wherein comparing the frequency variance with a threshold comprises comparing the frequency variance with a plurality of thresholds to determine the class of audio signal.

28. The non-transitory computer readable medium of claim 27, wherein the control code comprises:

a flag indicating whether or not the class of audio signal has changed from a last frame; and

a parameter indicating the class of audio signal if the flag indicates that the class of audio signal has changed from the last frame.

29. The non-transitory computer readable medium of claim 23, wherein the program further instructs the microprocessor to perform the step of varying the threshold with hysteresis.

30. The non-transitory computer readable medium of claim 23, wherein the program further instructs the microprocessor to perform the step of smoothing the frequency variance before determining the class of audio signal.

31. The non-transitory computer readable medium of claim 30, wherein the smoothing the frequency variance comprises performing a moving average of the frequency variance over a plurality of frames.