SYSTEMS, METHODS, APPARATUS, AND COMPUTER-READABLE MEDIA FOR NOISE INJECTION

• US 20120046955A1
• Filed: 08/16/2011
• Published: 02/23/2012
• Est. Priority Date: 08/17/2010
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Rajendran, Vivek, Krishnan, Venkatesh, Duni, Ethan Robert
• Granted Patent: US 9,208,792 B2
• Time in Patent Office: Days
• US Class Current: 704/500
• CPC Class Codes: G10L 19/028 Noise substitution, i.e. substituting non-tonal spectral components by noisy source comfort noise for discontinuous speech transmission G10L19/012

Abstract

A scheme for injecting noise at uncoded elements of a spectrum is controlled according to a measure of a distribution of energy of the original spectrum among the locations of the uncoded elements.

Claims

1. A method of processing an audio signal, said method comprising:

based on information from the audio signal, selecting one among a plurality of entries of a codebook;

determining locations, in a frequency domain, of zero-valued elements of a first signal that is based on the selected codebook entry;

calculating energy of the audio signal at the determined frequency-domain locations;

calculating a value of a measure of a distribution of the energy of the audio signal among the determined frequency-domain locations; and

based on said calculated energy and said calculated value, calculating a noise injection gain factor.

2. The method according to claim 1, wherein said selected codebook entry is based on a pattern of unit pulses.

3. The method according to claim 1, wherein said calculating a value of a measure of a distribution of the energy of the audio signal includes:

calculating an energy of an element of the audio signal at each of the determined frequency-domain locations; and

sorting the calculated energies of the elements.

4. The method according to claim 1, wherein said value of a measure of a distribution of energy is based on a relation between (A) a total energy of a proper subset of the elements of the audio signal at said determined frequency-domain locations and (B) a total energy of the elements of the audio signal at said determined frequency-domain locations.

5. The method according to claim 1, wherein said noise injection gain factor is based on a relation between (A) said calculated energy of the audio signal at the determined frequency-domain locations and (B) an energy of the audio signal in a frequency range that includes the determined frequency-domain locations.

6. The method according to claim 1, wherein said calculating the noise injection gain factor includes:

detecting that an initial value of the noise injection gain factor is not greater than a threshold value; and

clipping the initial value of the noise injection gain factor in response to said detecting.

7. The method according to claim 6, wherein said noise injection gain factor is based on a result of applying the calculated value of the measure of energy distribution to the clipped value.

8. The method according to claim 1, wherein said audio signal is a plurality of modified discrete cosine transform coefficients.

9. The method according to claim 1, wherein said audio signal is based on a residual of a linear prediction coding analysis of a second audio signal.

10. The method according to claim 9, wherein said noise injection gain factor is also based on a linear prediction coding gain, and

wherein said linear prediction coding gain is based on a set of coefficients produced by said linear prediction coding analysis of the second audio signal.

11. An apparatus for processing an audio signal, said apparatus comprising:

means for selecting one among a plurality of entries of a codebook, based on information from the audio signal;

means for determining locations, in a frequency domain, of zero-valued elements of a first signal that is based on the selected codebook entry;

means for calculating energy of the audio signal at the determined frequency-domain locations;

means for calculating a value of a measure of a distribution of the energy of the audio signal among the determined frequency-domain locations; and

means for calculating a noise injection gain factor based on said calculated energy and said calculated value.

12. The apparatus according to claim 11, wherein said selected codebook entry is based on a pattern of unit pulses.

13. The apparatus according to claim 11, wherein said means for calculating a value of a measure of a distribution of the energy of the audio signal includes:

means for calculating an energy of an element of the audio signal at each of the determined frequency-domain locations; and

means for sorting the calculated energies of the elements.

14. The apparatus according to claim 11, wherein said value of a measure of a distribution of energy is based on a relation between (A) a total energy of a proper subset of the elements of the audio signal at said determined frequency-domain locations and (B) a total energy of the elements of the audio signal at said determined frequency-domain locations.

15. The apparatus according to claim 11, wherein said noise injection gain factor is based on a relation between (A) said calculated energy of the audio signal at the determined frequency-domain locations and (B) an energy of the audio signal in a frequency range that includes the determined frequency-domain locations.

16. The apparatus according to claim 11, wherein said means for calculating the noise injection gain factor includes:

means for detecting that an initial value of the noise injection gain factor is not greater than a threshold value; and

means for clipping the initial value of the noise injection gain factor in response to said detecting.

17. The apparatus according to claim 16, wherein said noise injection gain factor is based on a result of applying the calculated value of the measure of energy distribution to the clipped value.

18. The apparatus according to claim 11, wherein said audio signal is a plurality of modified discrete cosine transform coefficients.

19. The apparatus according to claim 11, wherein said audio signal is based on a residual of a linear prediction coding analysis of a second audio signal.

20. The apparatus according to claim 19, wherein said noise injection gain factor is also based on a linear prediction coding gain, and

wherein said linear prediction coding gain is based on a set of coefficients produced by said linear prediction coding analysis of the second audio signal.

21. An apparatus for processing an audio signal, said apparatus comprising:

a vector quantizer configured to select one among a plurality of entries of a codebook, based on information from the audio signal;

a zero-value detector configured to determine locations, in a frequency domain, of zero-valued elements of a first signal that is based on the selected codebook entry;

an energy calculator configured to calculate energy of the audio signal at the determined frequency-domain locations;

a sparsity calculator configured to calculate a value of a measure of a distribution of the energy of the audio signal among the determined frequency-domain locations; and

a gain factor calculator configured to calculate a noise injection gain factor based on said calculated energy and said calculated value.

22. The apparatus according to claim 21, wherein said selected codebook entry is based on a pattern of unit pulses.

23. The apparatus according to claim 21, wherein said sparsity calculator is configured to calculate an energy of an element of the audio signal at each of the determined frequency-domain locations and to sort the calculated energies of the elements.

24. The apparatus according to claim 21, wherein said value of a measure of a distribution of energy is based on a relation between (A) a total energy of a proper subset of the elements of the audio signal at said determined frequency-domain locations and (B) a total energy of the elements of the audio signal at said determined frequency-domain locations.

25. The apparatus according to claim 21, wherein said noise injection gain factor is based on a relation between (A) said calculated energy of the audio signal at the determined frequency-domain locations and (B) an energy of the audio signal in a frequency range that includes the determined frequency-domain locations.

26. The apparatus according to claim 21, wherein said gain factor calculator is configured to detect that an initial value of the noise injection gain factor is not greater than a threshold value and to clip the initial value of the noise injection gain factor in response to said detecting.

27. The apparatus according to claim 26, wherein said noise injection gain factor is based on a result of applying the calculated value of the measure of energy distribution to the clipped value.

28. The apparatus according to claim 21, wherein said audio signal is a plurality of modified discrete cosine transform coefficients.

29. The apparatus according to claim 21, wherein said audio signal is based on a residual of a linear prediction coding analysis of a second audio signal.

30. The apparatus according to claim 29, wherein said noise injection gain factor is also based on a linear prediction coding gain, and

wherein said linear prediction coding gain is based on a set of coefficients produced by said linear prediction coding analysis of the second audio signal.

31. A non-transitory computer-readable storage medium having tangible features that cause a machine reading the features to:

select one among a plurality of entries of a codebook, based on information from the audio signal;

determine locations, in a frequency domain, of zero-valued elements of a first signal that is based on the selected codebook entry;

calculate energy of the audio signal at the determined frequency-domain locations;

calculate a value of a measure of a distribution of the energy of the audio signal among the determined frequency-domain locations; and

calculate a noise injection gain factor based on said calculated energy and said calculated value.