Method and Apparatus for Improving the Quality of Speech Signals

• US 20090132260A1
• Filed: 11/12/2008
• Published: 05/21/2009
• Est. Priority Date: 10/22/2003
• Status: Active Grant

• Current Assignee: Tellabs Operations Incorporated (Infinera Corp.)
• Original Assignee: Tellabs Operations Incorporated (Infinera Corp.)
• Inventors: Tanrikulu, Oguz
• Granted Patent: US 8,095,374 B2
• Time in Patent Office: Days
• US Class Current: 704/500
• CPC Class Codes: G10L 21/038 using band spreading techniques

Abstract

Methods and apparatus are disclosed to extend the bandwidth of a speech communication to yield a perceived higher quality speech communication for an enhanced user experience. In one aspect of the invention, for example, methods and apparatus can be used to extend the bandwidth of a speech communication beyond a band-limited region defined by the lowest limit and highest limit of the frequency spectrum by which such speech communication is otherwise characterized absent such bandwidth extension. In another aspect of the invention, for example, methods and apparatus can be used to substitute for corrupt, missing or lost components of a given speech communication, or to otherwise enhance the perceived quality of a speech communication, by extending the speech communication to include one or more artificially created points within the region defined by the lowest limit and highest limit of the frequency spectrum by which such speech communication is characterized. The result is a speech communication that is perceived to be of higher quality. The various aspects of the present invention can be applied, for example, to network devices or to end-terminal devices.

Claims

1. A network device comprising:

an input interface;

a generation unit configured to generate a bandwidth extended signal derived from a far-end speech communication signal received at the input interface; and

an output interface to which the bandwidth extended signal is provided.

2. The network device of claim 1 further comprising a decoder to decode the far-end speech communication signal.

3. The network device of claim 1 further comprising an encoder to encode the bandwidth extended signal.

4. The network device of claim 2 further comprising an encoder to encode the bandwidth extended signal.

5. The network device of claim 1 wherein the generation unit is configured to generate a derivative signal having at least one component at a frequency that is outside a bandwidth of the far-end speech communication signal, the at least one component being derived from the far-end speech communication signal, and wherein the generation unit includes a combiner configured to combine the derivative signal with the far-end speech communication signal to generate the bandwidth extended signal.

6. The network device of claim 5 further comprising a gain controller to determine a gain for the derivative signal.

7. The network device of claim 5 further comprising a delay element to add delay to the far-end speech communication signal that is combined with the derivative signal to generate to the bandwidth extended signal.

8. The network device of claim 1 wherein the input interface is adapted to receive a narrowband far-end speech communication signal and the output interface is adapted to provide a wideband bandwidth extended signal.

9. The network device of claim 1 wherein the input interface is adapted to receive a narrowband far-end speech communication signal and the output interface is adapted to provide a bandwidth extended signal having a bandwidth that is at least as broad as a wideband signal.

10. The network device of claim 1 wherein the input interface is adapted to receive a 4 KHz signal far-end speech communication signal and the output interface is adapted to provide a bandwidth extended signal including frequency of >

4 KHz.

11. The network device of claim 6 further comprising a voice activity detector to detect whether the far-end speech communication signal contains speech at a given point in time, and wherein the gain for the derivative signal determined by the gain controller differs depending upon whether speech is detected by the voice activity detector.

12. The network device of claim 6 further comprising a voice activity detector to determine an interval in the far-end speech communication signal when speech is not present, and wherein the gain controller is arranged to apply a different level of gain to the derivative signal during the interval as compared to a level of gain applied to the derivative signal prior to the interval.

13. The network device of claim 6 wherein the generation unit is adapted to determine the gain for the derivative signal as a function of determining a level of ambient noise at a near-end of a far-end speech communication represented by the far-end speech communication signal.

14. The network device of claim 13 wherein the method further includes:

receiving a near-end signal; and

determining the level of ambient noise at the near-end by reference to the near-end signal.

15. The network device of claim 14 wherein the level of ambient noise at the near-end is not determined by reference to the near-end signal at a given point in time when speech is detected in the near-end signal.

16. The network device of claim 14 wherein the level of ambient noise at the near-end is determined by reference to the near-end signal only during an interval when speech is not detected in the near-end signal.

17. The network device of claim 1 wherein the generation unit is adapted to generate a plurality of derivative signals each having at least one component at a frequency that is outside a bandwidth of the far-end speech communication signal, wherein such component is derived from the far-end speech communication signal, and wherein the generation unit includes a combiner configured to combine the derivative signals with the far-end speech communication signal to generate the bandwidth extended signal.

18. A network device based method for bandwidth extension, the method comprising:

receiving a signal including a far-end speech communication;

generating a bandwidth extended signal derived from the received signal; and

providing the bandwidth extended signal to an output of the network device.

19. The method of claim 18 further including decoding the received signal.

20. The method of claim 18 further including encoding the bandwidth extended signal to provide an encoded bandwidth extended signal at the output of the network device.

21. The method of claim 19 further comprising encoding the bandwidth extended signal to provide an encoded bandwidth extended signal at the output of the network device.

22. The method of claim 18 wherein generating a bandwidth extended signal includes:

filtering the received signal to generate a first signal having a frequency spectrum that is at least substantially confined to a first band-limited region;

generating a second signal by mapping at least one frequency component of the first signal to frequency spectrum that is outside the first band-limited region;

filtering the second signal to generate a third signal having a frequency spectrum that is at least substantially confined to a second band-limited region, wherein at least a portion of the second band-limited region includes frequency spectrum that is outside the first band-limited region; and

combining the third signal with the received signal to generate the bandwidth extended signal.

23. The method of claim 22 further comprising sampling the received signal to generate a sampled version of the received signal and wherein the filtering the received signal to generate a first signal includes filtering the sampled version of the received signal to generate the first signal.

24. The method of claim 22 further determining a gain for the third signal.

25. The method of claim 22 wherein the received signal that is combined with the third signal to generate the bandwidth extended signal is a delayed received signal, and further including delaying the received signal to generate the delayed received signal.

26. The method of claim 18 wherein the received signal is a narrowband signal and the bandwidth extended signal is a wideband signal.

27. The method of claim 18 wherein the received signal is a narrowband signal and the bandwidth extended signal has a bandwidth that is at least as broad as a wideband signal.

28. The method of claim 18 wherein the received signal is a 4 KHz signal and the bandwidth extended signal is a signal including frequency of >

4 KHz.

29. The method of claim 24 further comprising:

detecting whether the speech communication contains speech at a given point in time; and

determining a different gain for the gain for the third signal as a function of detecting the speech.

30. The method of claim 24 further comprising:

determining an interval in the speech communication when speech is not present; and

applying a different level of gain to the third signal during the interval as compared to a level of gain applied to the third signal prior to the interval.

31. The method of claim 24 further comprising determining the gain for the third signal as a function of determining a level of ambient noise at a near-end of the far-end speech communication.

32. The method of claim 31 further comprising:

receiving a near-end signal; and

determining the level of ambient noise at the near-end by reference to the near-end signal.

33. The method of claim 32 wherein the level of ambient noise at the near-end is not determined by reference to the near-end signal at a given point in time when speech is detected in the near-end signal.

34. The method of claim 32 wherein the level of ambient noise at the near-end is determined by reference to the near-end signal only during an interval when speech is not detected in the near-end signal.

35. The method of claim 18 further including generating a bandwidth extended signal as a function of generating a plurality of derivative signals each having at least one component at a frequency that is outside a bandwidth of the received signal, wherein such at least one component is derived from the received signal;

and combining the derivative signals with the received signal to generate the bandwidth extended signal.

36. A network device based method, the method comprising:

receiving an input signal;

generating an output signal, the output signal representing a wider bandwidth version of a speech communication represented by the input signal; and

providing the output signal to an output of the network device.

37. The method of claim 36 further comprising decoding the input signal.

38. The method of claim 36 further comprising encoding the output signal.

39. The method of claim 37 further comprising encoding the output signal.

40. The method of claim 36 further including generating an output signal as a function of:

filtering the input signal to generate a first filtered signal having a frequency spectrum that is at least substantially confined to a first band-limited region;

generating a derivative signal having at least one component at a frequency that is outside the first band-limited region, wherein such at least one component of the derivative signal is derived from at least one characteristic of the first filtered signal;

filtering the derivative signal to generate a second filtered signal having a frequency spectrum that is at least substantially confined to a second band-limited region, wherein at least a portion of the second band-limited region includes frequency spectrum that is outside the first band-limited region; and

combining the second filtered signal with the input signal to generate the output signal.

41. The method of claim 36 further including generating an output signal as a function of generating a derivative signal having at least one component at a frequency that is outside a bandwidth of the input signal, the at least one component being derived from the input signal;

and combining the derivative signal with the input signal to generate the output signal.

42. The method of claim 40 further including sampling the input signal to generate a sampled version of the input signal, and further including filtering the input signal to generate a first filtered signal as a function of filtering the sampled version of the input signal to generate the first filtered signal.

43. The method of claim 41 further including determining the gain for the derivative signal.

44. The method of claim 41 wherein the input signal that is combined with the derivative signal to generate the output signal is a delayed input signal, and further including delaying the input signal to generate the delayed input signal.

45. The method of claim 36 wherein the input signal is a narrowband signal and the output signal is a wideband signal.

46. The method of claim 36 wherein the input signal is a narrowband signal and the output signal has a bandwidth that is at least as broad as a wideband signal.

47. The method of claim 36 wherein the input signal is a 4 KHz signal and the output signal is a signal including frequency of >

4 KHz.

48. The method of claim 43 further comprising:

detecting whether the input signal contains speech at a given point in time; and

determining a different gain for the gain for the derivative signal as a function of detecting the speech.

49. The method of claim 43 further including:

determining an interval in the input signal when speech is not present; and

applying a different level of gain to the derivative signal during the interval as compared to a level of gain applied to the derivative signal prior to the interval.

50. The method of claim 43 wherein the input signal represents a far-end speech communication, and further including determining the gain for the derivative signal as a function of determining a level of ambient noise at a near-end of the far-end speech communication.

51. The method of claim 50 further comprising:

receiving a near-end signal; and

determining the level of ambient noise at the near-end by reference to the near-end signal.

52. The method of claim 51 wherein the level of ambient noise at the near-end is not newly determined by reference to the near-end signal at a given point in time when speech is detected in the near-end signal.

53. The method of claim 51, wherein the level of ambient noise at the near-end is newly determined by reference to the near-end signal only during an interval when speech is not detected in the near-end signal.

54. The method of claim 36 further including generating an output signal as a function of:

generating a plurality of derivative signals each having at least one component at a frequency that is outside a bandwidth of the input signal, wherein such at least one component is derived from the input signal; and

combining the derivative signals with the input signal to generate the output signal.

55. A network device based method, the method comprising:

receiving an input signal at an input interface of the network device;

decoding the input signal;

determining an interval in the input signal when speech is not present in the input signal;

generating a derivative signal having at least one component at a frequency that is outside a bandwidth of the input signal, the at least one component being derived from the decoded input signal;

determining a gain for the derivative signal to generate a gain-determined derivative signal, a lower level of gain being determined for the derivative signal during the interval as compared to a level of gain applied to the derivative signal prior to the interval;

delaying the decoded input signal to generate a delayed input signal;

combining the gain-determined derivative signal with the delayed input signal to generate an output signal, the output signal representing a wider bandwidth version of a speech communication represented by the input signal;

encoding the output signal; and

providing the encoded output signal to an output interface of the network device.