System and Method for Frequency Domain Audio Post-processing Based on Perceptual Masking

• US 20110002266A1
• Filed: 05/04/2010
• Published: 01/06/2011
• Est. Priority Date: 05/05/2009
• Status: Active Grant

• Current Assignee: Huawei Technologies Co., Ltd. (Huawei Investment & Holding Co., Ltd.)
• Original Assignee: GH Innovation Incorporated
• Inventors: Gao, Yang
• Granted Patent: US 8,391,212 B2
• Time in Patent Office: Days
• US Class Current: 370/328
• 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 an embodiment, a method of frequency domain post-processing is disclosed. The method includes applying adaptive modification gain factor to each frequency coefficient, and determining gain factors based on Local Masking Magnitude and Local Masked Magnitude.

Claims

1. A method of post-processing of a frequency domain audio signal using an audio post-processor, the method comprising:

applying adaptive modification gain factor to each frequency coefficient of the frequency domain audio signal; and

determining gain factors based on Local Masking Magnitude and Local Masked Magnitude.

2. The method of claim 1, wherein the audio post-processor performs post-processing in a Modified Discrete Cosine Transform (MDCT) domain or a Fast Fourier Transform (FFT) domain.

3. The method of claim 1, wherein the Local Masking Magnitude and Local Masked Magnitude are estimated according to perceptual masking effects.

4. The method of claim 3, wherein the Local Masking Magnitude is estimated by taking a weighted sum around a specific frequency at i:

5. The method of claim 4, wherein Local Masked Magnitude M₁(i) is estimated by taking a weighted sum the specific frequency at i:

6. A method of post-processing of a frequency domain audio signal using an audio post-processor, the method comprising:

applying adaptive modification gain factor to each frequency coefficient of the frequency domain audio signal; and

determining gain factors based on Local Masking Magnitude, Local Masked Magnitude, and Average Magnitude.

7. The method of claim 6, wherein the Average Magnitude is calculated on a whole spectrum band of the frequency domain audio signal.

8. The method of claim 7, wherein the Average Magnitude is calculated by:

9. The method of claim 7, wherein an initial gain factor for each frequency is

10. The method of claim 9, wherein:

11. The method of claim 10, wherein first frequency dependent weighting window is asymmetric and the second frequency dependent weighting window is asymmetric.

12. The method of claim 10, wherein gain factors are normalized according to:

Gain₁(i)=Gain₀(i)·

Norm,

wherein normalization factor Norm is defined as,

13. The method of claim 12, wherein the normalized gain factors can be controlled by parameter β

such that;

Gain₂(i)=β

·

Gain₁(i)+(1−

β

)

wherein (0≦

β

≦

1), β

is a parameter that controls strong post-processing or weak post-processing.

14. The method of claim 13, wherein β

is replaced by a smoothed controlling parameter β

, such that;

β

0.75 β

+0.25β

.

15. The method of claim 6, wherein determined gain factors are multiplied with the frequency coefficients to produce post-processed frequency coefficients.

16. The method of claim 6, further comprising receiving the frequency domain audio signal from a voice over internet protocol (VOIP) network.

17. The method of claim 6, further comprising receiving the frequency domain audio signal from a mobile telephone network.

18. The method of claim 6, further comprising converting the post-processed frequency domain signal into a time domain audio signal.

19. A system for receiving a frequency domain audio signal, the system comprising a post-processor configured to:

apply an adaptive modification gain factor to each frequency coefficient of the frequency domain audio signal; and

determine gain factors based on Local Masking Magnitude and Local Masked Magnitude and Average Magnitude.

20. The system of claim 19, wherein the post-processor calculates an initial gain factor Gain₀(i) for each frequency according to:

21. The system of claim 20, wherein:

22. The system of claim 19, wherein the system is configured to operate over a voice over internet protocol (VOIP) system or a cellular telephone network.

23. The system of claim 19, further comprising an audio decoder configured to receive audio parameters and produce the audio signal based on the received audio parameters.

24. The system of claim 19, wherein the receiver is further configured to convert an output of the post-processor to an output audio signal.

25. The system of claim 24, wherein the output audio signal is configured to be coupled to a loudspeaker.