Systems and Methods of Performing Noise Modulation and Gain Adjustment

• US 20140229172A1
• Filed: 08/28/2013
• Published: 08/14/2014
• Est. Priority Date: 02/08/2013
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Atti, Venkatraman Srinivasa, Krishnan, Venkatash
• Granted Patent: US 9,601,125 B2
• Time in Patent Office: Days
• US Class Current: 704/225
• CPC Class Codes: G10L 19/032 Quantisation or dequantisation of spectral components
• CPC Class Codes: G10L 19/035 Scalar quantisation
• 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 19/167 Audio streaming, i.e. formatting and decoding of an encoded audio signal representation into a data stream for transmission or storage purposes
• CPC Class Codes: G10L 2019/0003 Backward prediction of gain
• CPC Class Codes: G10L 21/038 using band spreading techniques
• CPC Class Codes: H03G 3/301 the gain being continuously variable
• CPC Class Codes: H03G 3/3089 Control of digital or coded signals

Abstract

A method includes receiving a first value of a mixing factor. The first value corresponds to a first portion of an audio signal received at an audio encoder. The method includes receiving a second value of the mixing factor. The second value corresponds to a second portion of the audio signal. The method also includes generating a third value of the mixing factor at least partially based on the first value and the second value and mixing an excitation signal with modulated noise based on the third value. Another method includes determining a first set of spectral frequency values corresponding to an audio signal and determining a second set of spectral frequency values that approximates the first set of spectral frequency values. A gain value corresponding to at least a portion of the audio signal is adjusted based on a difference between the first set and the second set.

Claims

1. A method comprising:

receiving a first value of a mixing factor, the first value corresponding to a first portion of an audio signal received at an audio encoder;

receiving a second value of the mixing factor, the second value corresponding to a second portion of the audio signal;

generating a third value of the mixing factor at least partially based on the first value and the second value; and

mixing an excitation signal with modulated noise based on the third value of the mixing factor.

2. The method of claim 1, further comprising generating a high-band excitation signal corresponding to a high-band portion of the audio signal, wherein the high-band excitation signal is generated based on combining the modulated noise and the excitation signal, wherein the excitation signal corresponds to a transformed version of a low-band excitation signal, the low-band excitation signal corresponding to a low-band portion of the audio signal.

3. The method of claim 2, wherein the high-band excitation signal comprises a weighted sum of the modulated noise and the transformed version of the low-band excitation signal.

4. The method of claim 1, wherein the first value is generated based on a low-band portion of a first sub-frame of the audio signal and wherein the second value is generated based on a low-band portion of a second sub-frame of the audio signal.

5. The method of claim 1, wherein generating the third value comprises determining a weighted sum of the first value and the second value.

6. The method of claim 5, wherein a first weight applied to the first value and a second weight applied to the second value are determined based on high-band energy fluctuation of the audio signal.

7. The method of claim 6, wherein the first weight and the second weight are determined based on a first high-band energy value corresponding to the first portion and further based on a second high-band energy value corresponding to the second portion.

8. The method of claim 7, wherein the first weight is selected to be greater than the second weight in response to the first high-band energy value exceeding a first threshold or in response to the second high-band energy value exceeding a second threshold, wherein the first threshold corresponds to the second high-band energy value scaled by a scaling factor, and wherein the second threshold corresponds to the first high-band energy value scaled by the scaling factor.

9. The method of claim 1, wherein generating the third value is further based on a spectral distortion corresponding to the audio signal.

10. The method of claim 1, wherein generating the third value is further based on an indication of a coding type corresponding to the audio signal.

11. The method of claim 1, wherein the first portion comprises a first sub-frame of the audio signal and wherein the second portion comprises a second sub-frame of the audio signal.

12. The method of claim 11, wherein the first sub-frame and the second sub-frame are in a single frame of the audio signal.

13. The method of claim 11, wherein the first sub-frame and the second sub-frames are in different frames of the audio signal.

14. A method comprising:

determining a first set of spectral frequency values corresponding to an audio signal;

determining a second set of spectral frequency values that approximates the first set of spectral frequency values; and

adjusting a gain value corresponding to at least a portion of the audio signal based on a difference between the first set and the second set.

15. The method of claim 14, further comprising estimating a spectral distortion corresponding to the difference between the first set and the second set.

16. The method of claim 15, wherein the spectral distortion is determined according to a mean square error of values in the second set of spectral frequency values as compared to values in the first set of spectral frequency values.

17. The method of claim 15, wherein the spectral distortion is determined according to an absolute difference between values in the second set of spectral frequency values as compared to values in the first set of spectral frequency values.

18. The method of claim 14, wherein the first set of spectral frequency values comprises line spectral frequency (LSF) values, and wherein the second set of spectral frequency values comprises quantized LSF values.

19. The method of claim 14, wherein the first set of spectral frequency values comprises linear prediction coefficient (LPC) values, and wherein the second set of spectral frequency values comprises quantized LPC values.

20. The method of claim 14, further comprising determining the second set of spectral frequency values by searching a codebook based on the first set of spectral frequency values.

21. The method of claim 14, wherein the gain value corresponds to a frame gain of a frame of the audio signal, and wherein adjusting the gain value comprises:

determining a spectral distortion between the first set of spectral frequency values and the second set of spectral frequency values;

determining a gain factor based on the spectral distortion; and

adjusting the frame gain by applying the gain factor to the frame gain.

22. The method of claim 21, wherein the gain factor is determined according to a mapping of spectral distortion values to gain factor values.

23. The method of claim 22, wherein a portion of the mapping defines that an increase in spectral distortion value corresponds to a decrease in gain factor value.

24. The method of claim 22, wherein the mapping is at least partially based on spectral distortion values corresponding to outliers of a probability distribution function.

25. An apparatus comprising:

a filter configured to generate a third value of a mixing factor at least partially based on a first value of the mixing factor and a second value of the mixing factor, wherein the first value corresponds to a first portion of an audio signal and wherein the second value corresponds to a second portion of the audio signal; and

a mixer configured to receive the third value and to generate a high-band excitation signal corresponding to a high-band portion of the audio signal by generating modulated noise and combining the modulated noise and a transformed version of a low-band excitation signal, the low-band excitation signal corresponding to a low-band portion of the audio signal,

wherein the mixer is configured to combine the modulated noise and the transformed version of the low-band excitation signal based on the third value.

26. The apparatus of claim 25, wherein the filter is configured to determine a weighted sum of the first value and the second value.

27. The apparatus of claim 26, wherein a first weight applied to the first value and a second weight applied to the second value are determined based on high-band energy fluctuation of the audio signal.

28. The apparatus of claim 27, wherein the first weight and the second weight are determined based on a first high-band energy value corresponding to the first portion and further based on a second high-band energy value corresponding to the second portion.

29. The apparatus of claim 28, wherein the first weight is selected to be greater than the second weight in response to the first high-band energy value exceeding a first threshold or in response to the second high-band energy value exceeding a second threshold, wherein the first threshold corresponds to the second high-band energy value scaled by a scaling factor, and wherein the second threshold corresponds to the first high-band energy value scaled by the scaling factor.

30. The apparatus of claim 25, wherein generating the third value is further based on a spectral distortion corresponding to the audio signal.

31. The apparatus of claim 25, wherein generating the third value is further based on an indication of a coding type corresponding to the audio signal.

32. An apparatus comprising:

means for generating a third value of a mixing factor at least partially based on a first value of the mixing factor and a second value of the mixing factor, wherein the first value corresponds to a first portion of an audio signal received at an audio encoder and wherein the second value corresponds to a second portion of the audio signal; and

means for generating a high-band excitation signal corresponding to a high-band portion of the audio signal by combining modulated noise and a transformed version of a low-band excitation signal, the low-band excitation signal corresponding to a low-band portion of the audio signal,

wherein the means for generating is configured to combine the modulated noise and the transformed version of the low-band excitation signal based on the third value.

33. The apparatus of claim 32, wherein a first weight applied to the first value and a second weight applied to the second value are determined based on high-band energy fluctuation of the audio signal.

34. The apparatus of claim 32, wherein the third value is generated further based on a spectral distortion corresponding to the audio signal.

35. The apparatus of claim 32, wherein the third value is generated further based on an indication of a coding type corresponding to the audio signal.

36. A non-transitory computer-readable medium comprising instructions that, when executed by a computer, cause the computer to:

receive a first value of a mixing factor, the first value corresponding to a first portion of an audio signal received at an audio encoder;

receive a second value of the mixing factor, the second value corresponding to a second portion of the audio signal;

generate a third value of the mixing factor at least partially based on the first value and the second value; and

mix an excitation signal with modulated noise based on the third value of the mixing factor.

37. The computer-readable medium of claim 36, further comprising instructions that, when executed by the computer, cause the computer to generate a high-band excitation signal corresponding to a high-band portion of the audio signal, wherein the high-band excitation signal is generated based on combining the modulated noise and the excitation signal, wherein the excitation signal corresponds to a transformed version of a low-band excitation signal, the low-band excitation signal corresponding to a low-band portion of the audio signal.

38. The computer-readable medium of claim 37, wherein the high-band excitation signal comprises a weighted sum of the modulated noise and the transformed version of the low-band excitation signal.

39. The computer-readable medium of claim 36, wherein the first value is generated based on a low-band portion of a first sub-frame of the audio signal and wherein the second value is generated based on a low-band portion of a second sub-frame of the audio signal.

40. An apparatus comprising:

an analysis filter configured to determine a first set of spectral frequency values corresponding to an audio signal;

a quantizer configured to generate a second set of spectral frequency values that approximates the first set of spectral frequency values; and

a gain circuit configured to adjust a gain value corresponding to at least a portion of the audio signal based on a difference between the first set and the second set.

41. The apparatus of claim 40, further comprising a spectral distortion calculator configured to estimate a spectral distortion corresponding to the difference between the first set and the second set.

42. The apparatus of claim 41, wherein the spectral distortion calculator is configured to determine the spectral distortion according to a mean square error of values in the second set of spectral frequency values as compared to values in the first set of spectral frequency values.

43. The apparatus of claim 41, wherein the spectral distortion calculator is configured to determine the spectral distortion according to an absolute difference between values in the second set of spectral frequency values as compared to values in the first set of spectral frequency values.

44. An apparatus comprising:

means for determining a first set of spectral frequency values corresponding to an audio signal;

means for generating a second set of spectral frequency values that approximates the first set of spectral frequency values; and

means for adjusting a gain value corresponding to at least a portion of the audio signal based on a difference between the first set and the second set.

45. The apparatus of claim 44, wherein the first set of spectral frequency values comprises line spectral frequency (LSF) values, and wherein the second set of spectral frequency values comprises quantized LSF values.

46. The apparatus of claim 44, wherein the first set of spectral frequency values comprises linear prediction coefficient (LPC) values, and wherein the second set of spectral frequency values comprises quantized LPC values.

47. The apparatus of claim 44, further comprising means for determining the second set of spectral frequency values by searching a codebook based on the first set of spectral frequency values.

48. A non-transitory computer-readable medium comprising instructions that, when executed by the computer, cause the computer to:

determine a first set of spectral frequency values corresponding to an audio signal;

determine a second set of spectral frequency values that approximates the first set of spectral frequency values; and

adjust a gain value corresponding to at least a portion of the audio signal based on a difference between the first set and the second set.

49. The computer-readable medium of claim 48, wherein the gain value corresponds to a frame gain of a frame of the audio signal, and wherein the instructions to cause the computer to adjust the gain value comprise instructions to cause the computer to:

determine a spectral distortion between the first set of spectral frequency values and the second set of spectral frequency values;

determine a gain factor based on the spectral distortion; and

adjust the frame gain by applying the gain factor to the frame gain.