Systems, methods, apparatus, and computer-readable media for far-field multi-source tracking and separation

1. An apparatus for processing a multichannel signal, said apparatus comprising:

a filter bank having (A) a first filter configured to apply a plurality of first coefficients to a first audio signal that is based on the multichannel signal to produce a first output signal and (B) a second filter configured to apply a plurality of second coefficients to a second audio signal that is based on the multichannel signal to produce a second output signal;

a filter orientation module configured to produce an initial set of values for the plurality of first coefficients, based on a first source direction, and to produce an initial set of values for the plurality of second coefficients, based on a second source direction that is different than the first source direction;

a processor; and

a filter updating module executed by the processor and configured (A) to determine, based on a plurality of filter responses at corresponding directions, a filter response that has a specified property, and (B) to update the initial set of values for the plurality of first coefficients, based on the first output signal and the second output signal and said filter response that has the specified property, wherein said specified property is a maximum value among said plurality of filter responses, and wherein updating the initial set of values for the plurality of first coefficients comprises adapting the initial set of values for the plurality of first coefficients based on the first output signal and the second output signal to produce an adapted set of values for the plurality of first coefficients, and normalizing the adapted set of values for the plurality of first coefficients based on the filter response that has the maximum value in order to produce a desired gain response with respect to direction.

2. The apparatus according to claim 1 , wherein each filter response of said plurality of filter responses is a filter response, at said corresponding direction, of a set of values that is based on the initial set of values for the plurality of first coefficients.

3. The apparatus according to claim 1 , wherein said filter updating module is configured to calculate a determined filter response that has a value at each frequency of a plurality of frequencies, and

wherein said calculating the determined filter response includes performing said determining at each frequency of the plurality of frequencies, and

wherein, at each frequency of the plurality of frequencies, said value of said determined filter response is said filter response that has the specified property among a plurality of filter responses at the frequency.

4. The apparatus according to claim 3 , wherein, at each frequency of the plurality of frequencies, said value of said determined filter response is a maximum value among said plurality of filter responses at the frequency.

5. The apparatus according to claim 3 , wherein said value of said determined filter response at a first frequency of the plurality of frequencies is a filter response in a first direction, and

wherein said value of said determined filter response at a second frequency of the plurality of frequencies is a filter response in a second direction that is different than the first direction.

6. The apparatus according to claim 1 , wherein said adapted set of values for the plurality of first coefficients includes (A) a first plurality of adapted values that correspond to a first frequency of said plurality of frequencies and (B) a second plurality of adapted values that correspond to a second frequency of said plurality of frequencies and said second frequency being different from said first frequency of said plurality of frequencies, and

wherein said normalizing comprises (A) normalizing each value of said first plurality of adapted values, based on said value of said determined filter response that corresponds to said first frequency of said plurality of frequencies, and (B) normalizing each value of said second plurality of adapted values, based on said value of said determined filter response that corresponds to said second frequency of said plurality of frequencies.

7. The apparatus according to claim 1 , wherein each value of the updated set of values for the plurality of first coefficients corresponds to a different value of the initial set of values for the plurality of first coefficients and to a frequency component of the multichannel signal, and

wherein each value of the updated set of values for the plurality of first coefficients that corresponds to a frequency component in a first frequency range has the same value as said corresponding value of the initial set of values for the plurality of first coefficients.

8. The apparatus according to claim 1 , wherein each of said plurality of the first and second coefficients corresponds to one among a plurality of frequency components of the multichannel signal.

9. The apparatus according to claim 1 , wherein the initial set of values for the plurality of first coefficients describes a beam oriented in the first source direction.

10. The apparatus according to claim 1 , wherein said filter updating module is configured to update the initial set of values for the plurality of first coefficients according to a result of applying a nonlinear bounded function to frequency components of the first and second output signals.

11. The apparatus according to claim 1 , wherein said filter updating module is configured to update the initial set of values for the plurality of first coefficients according to a blind source separation learning rule.

12. The apparatus according to claim 1 , wherein said updating the initial set of values for the plurality of first coefficients is based on a spatial constraint, and wherein said spatial constraint is based on the second source direction.

13. The apparatus according to claim 1 , wherein said updating the initial set of values for the plurality of first coefficients includes attenuating a filter response of the plurality of first coefficients in the second source direction relative to a filter response of the plurality of first coefficients in the first source direction.

14. The apparatus according to claim 1 , wherein said apparatus comprises a direction estimation module configured to calculate the first source direction based on information within the multichannel signal.

15. The apparatus according to claim 1 , wherein said apparatus comprises a microphone array including a plurality of microphones, and

wherein each channel of the multichannel signal is based on a signal produced by a different corresponding microphone of the plurality of microphones, and

wherein the microphone array has an aperture of at least twenty centimeters.

16. The apparatus according to claim 1 , wherein said apparatus comprises a microphone array including a plurality of microphones, and

wherein each channel of the multichannel signal is based on a signal produced by a different corresponding microphone of the plurality of microphones, and

wherein a distance between a first pair of adjacent microphones of the microphone array differs from a distance between a second pair of adjacent microphones of the microphone array.

17. The apparatus according to claim 1 , wherein said filter bank includes a third filter configured to apply a plurality of third coefficients to the multichannel signal to produce a third output signal, and

wherein said apparatus includes a noise reduction module configured to perform a noise reduction operation on the first output signal, based on information from the third output signal, to produce a dereverberated signal.

18. The apparatus according to claim 17 , wherein each channel of said multichannel signal is based on a signal produced by a corresponding microphone of a plurality of microphones of an array, and

wherein said filter orientation module is configured to produce a set of values for the plurality of third coefficients, based on a direction of an axis of the array.

19. The apparatus according to claim 1 , wherein said filter updating module is configured to update the initial set of values for the plurality of first coefficients in a frequency domain, and

wherein said filter bank is configured to apply the plurality of first coefficients to the first audio signal in the time domain.

20. A method of processing a multichannel signal by an apparatus, said method comprising:

applying a plurality of first coefficients to a first audio signal that is based on the multichannel signal to produce a first output signal, wherein the multichannel signal is received by a microphone array including a plurality of microphones;

applying a plurality of second coefficients to a second audio signal that is based on the multichannel signal to produce a second output signal;

producing an initial set of values for the plurality of first coefficients, based on a first source direction;

producing an initial set of values for the plurality of second coefficients, based on a second source direction that is different than the first source direction;

determining, based on a plurality of filter responses at corresponding directions, a filter response that has a specified property; and

updating, using a processor, the initial set of values for the plurality of first coefficients, based on the first output signal and the second output signal and said filter response that has the specified property, wherein said specified property is a maximum value among said plurality of filter responses, wherein updating the initial set of values for the plurality of first coefficients comprises adapting the initial set of values for the plurality of first coefficients based on the first output signal and the second output signal to produce an adapted set of values for the plurality of first coefficients, and normalizing the adapted set of values for the plurality of first coefficients based on the filter response that has the maximum value in order to produce a desired gain response with respect to direction.

21. The method according to claim 20 , wherein each filter response of said plurality of filter responses is a filter response, at said corresponding direction, of a set of values that is based on the initial set of values for the plurality of first coefficients.

22. The method according to claim 20 , wherein said method includes calculating a determined filter response that has a value at each frequency of a plurality of frequencies, and

wherein said calculating the determined filter response includes performing said determining at each frequency of the plurality of frequencies, and

wherein, at each frequency of the plurality of frequencies, said value of said determined filter response is said filter response that has the specified property among a plurality of filter responses at the frequency.

23. The method according to claim 22 , wherein, at each frequency of the plurality of frequencies, said value of said determined filter response is a maximum value among said plurality of filter responses at the frequency.

24. The method according to claim 22 , wherein said value of said determined filter response at a first frequency of the plurality of frequencies is a filter response in a first direction, and

wherein said value of said determined filter response at a second frequency of the plurality of frequencies is a filter response in a second direction that is different than the first direction.

25. The method according to claim 20 , wherein said adapted set of values for the plurality of first coefficients includes (A) a first plurality of adapted values that correspond to a first frequency of said plurality of frequencies and (B) a second plurality of adapted values that correspond to a second frequency of said plurality of frequencies and said second frequency being different from said first frequency of said plurality of frequencies, and

wherein said normalizing comprises (A) normalizing each value of said first plurality of adapted values, based on said value of said determined filter response that corresponds to said first frequency of said plurality of frequencies, and (B) normalizing each value of said second plurality of adapted values, based on said value of said determined filter response that corresponds to said second frequency of said plurality of frequencies.

26. The method according to claim 1 , wherein each value of the updated set of values for the plurality of first coefficients corresponds to a different value of the initial set of values for the plurality of first coefficients and to a frequency component of the multichannel signal, and

wherein each value of the updated set of values for the plurality of first coefficients that corresponds to a frequency component in a first frequency range has the same value as said corresponding value of the initial set of values for the plurality of first coefficients.

27. The method according to claim 20 , wherein each of said plurality of the first and second coefficients corresponds to one among a plurality of frequency components of the multichannel signal.

28. The method according to claim 20 , wherein the initial set of values for the plurality of first coefficients describes a beam oriented in the first source direction.

29. The method according to claim 20 , wherein said updating the initial set of values for the plurality of first coefficients is performed according to a result of applying a nonlinear bounded function to frequency components of the first and second output signals.

30. The method according to claim 20 , wherein said updating the initial set of values for the plurality of first coefficients is performed according to a blind source separation learning rule.

31. The method according to claim 20 , wherein said updating the initial set of values for the plurality of first coefficients is based on a spatial constraint, and

wherein said spatial constraint is based on the second source direction.

32. The method according to claim 20 , wherein said updating the initial set of values for the plurality of first coefficients includes attenuating a filter response of the plurality of first coefficients in the second source direction relative to a filter response of the plurality of first coefficients in the first source direction.

33. The method according to claim 20 , wherein said method includes calculating the first source direction based on information within the multichannel signal.

34. The method according to claim 20 , wherein each channel of the multichannel signal is based on a signal produced by a different corresponding microphone of the plurality of microphones of the microphone array, and

wherein the microphone array has an aperture of at least twenty centimeters.

35. The method according to claim 20 , wherein each channel of the multichannel signal is based on a signal produced by a different corresponding microphone of the plurality of microphones of the microphone array, and

wherein a distance between a first pair of adjacent microphones of the microphone array differs from a distance between a second pair of adjacent microphones of the microphone array.

36. The method according to claim 20 , wherein said method includes:

applying a plurality of third coefficients to the multichannel signal to produce a third output signal; and

performing a noise reduction operation on the first output signal, based on information from the third output signal, to produce a dereverberated signal.

37. The method according to claim 36 , wherein each channel of said multichannel signal is based on a signal produced by a corresponding microphone of the plurality of microphones of the microphone array, and

wherein said method includes producing a set of values for the plurality of third coefficients, based on a direction of an axis of the array.

38. The method according to claim 20 , wherein said updating includes updating the initial set of values for the plurality of first coefficients in a frequency domain, and

wherein said applying the plurality of first coefficients to the first audio signal is performed in the time domain.

39. An apparatus for processing a multichannel signal, comprising:

means for applying a plurality of first coefficients to a first audio signal that is based on the multichannel signal to produce a first output signal and for applying a plurality of second coefficients to a second audio signal that is based on the multichannel signal to produce a second output signal, wherein the multichannel signal is based on an acoustic signal;

means for producing an initial set of values for the plurality of first coefficients, based on a first source direction and for producing an initial set of values for the plurality of second coefficients, based on a second source direction that is different than the first source direction;

means for determining, based on a plurality of filter responses at corresponding directions, a filter response that has a specified property; and

means for updating, using a processor, the initial set of values for the plurality of first coefficients, based on the first output signal and the second output signal and said filter response that has the specified property, wherein said specified property is a maximum value among said plurality of filter responses, and wherein the means for updating the initial set of values for the plurality of first coefficients comprises means for adapting the initial set of values for the plurality of first coefficients based on the first output signal and the second output signal to produce an adapted set of values for the plurality of first coefficients, and means for normalizing the adapted set of values for the plurality of first coefficients based on the filter response that has the maximum value in order to produce a desired gain filter response with respect to direction.

40. A non-transitory computer-readable storage medium comprising tangible features that when read by a processor cause the processor to:

apply a plurality of first coefficients to a first audio signal that is based on a multichannel signal to produce a first output signal;

apply a plurality of second coefficients to a second audio signal that is based on the multichannel signal to produce a second output signal, wherein the multichannel signal is based on an acoustic signal;

produce an initial set of values for the plurality of first coefficients, based on a first source direction;

produce an initial set of values for the plurality of second coefficients, based on a second source direction that is different than the first source direction;

determine, based on a plurality of filter responses at corresponding directions, a filter response that has a specified property; and

update the initial set of values for the plurality of first coefficients, based on the first output signal and the second output signal and said filter response that has the specified property, wherein said specified property is a maximum value among said plurality of filter responses, and wherein updating the initial set of values for the plurality of first coefficients comprises adapting the initial set of values for the plurality of first coefficients based on the first output signal and the second output signal to produce an adapted set of values for the plurality of first coefficients, and normalizing the adapted set of values for the plurality of first coefficients based on the filter response that has the maximum value in order to produce a desired gain filter response with respect to direction.