Controlling echo during double-talk in a voice conference

• US 8,238,548 B2
• Filed: 02/08/2008
• Issued: 08/07/2012
• Est. Priority Date: 02/08/2008
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Frauenthal, James C., Ramalho, Michael A., Skrabutenas, Gary, Wildfeuer, Herbert
• Primary Examiner(s): Tsang, Fan
• Assistant Examiner(s): LYTLE, JEFFREY P
• Application Number:
  US12/028,594
• Publication Number:
  US 20090202063A1
• Time in Patent Office: 1,642 Days
• Field of Search: 370260-269, 370/288
• US Class Current: 379/406.16
• CPC Class Codes: H04M 9/08 Two-way loud-speaking telephone systems with means for conditioning the signal, e.g. for suppressing echoes for one or both directions of traffic

Abstract

An echo canceller apparatus comprises a receive side attenuator coupled in a receive side signal path that is configured to couple from a conference call bridge to a caller; a convolution processor coupled to the receive side signal path at a convolution processor pick-off point; a double-talk detector coupled to the receive side signal path and to a sending side signal path that is configured to couple from the caller to the conference call bridge; and logic coupled to the receive side attenuator which when executed is responsive to a double-talk condition detected by the double-talk detector and operable to determine a level of echo canceled by the convolution processor, to determine an additional amount of attenuation to introduce, and to activate the receive side attenuator to introduce the additional attenuation.

Claims

1. An echo canceller apparatus, comprising:

a receive side attenuator coupled in a receive side signal path that is configured to couple from a conference call bridge to a caller;

a convolution processor coupled to the receive side signal path at a pick-off point;

a double-talk detector coupled to the receive side signal path and to a sending side signal path that is configured to couple from the caller to the conference call bridge;

logic coupled to the receive side attenuator which is configured to;

responsive to a double-talk condition detected by the double-talk detector,

determine a level of echo canceled by the convolution processor,

determine an additional amount of attenuation to introduce to a caller input signal, and

activate the receive side attenuator to introduce the additional attenuation to the caller input signal;

wherein the caller input signal is provided to a caller causing the double-talk condition.

2. The apparatus of claim 1, further comprising logic which when executed by the processor is operable to disable the receive side attenuator when the double-talk condition ends, to detect a further occurrence of double-talk, and in response thereto, to stops or slows the adaptation of the convolution processor, deactivate a non-linear processor that is coupled in the sending side signal path, and to again activate the receive side attenuator to introduce the additional attenuation.

3. The apparatus of claim 1, wherein the receive side attenuator is coupled in the receive side signal path before the convolution processor pick-off point.

4. The apparatus of claim 1, wherein the receive side attenuator is coupled in the receive side signal path after the convolution processor pick-off point.

5. The apparatus of claim 1, wherein the receive side attenuator is in the conference call bridge.

6. The apparatus of claim 1, further comprising a first control signal path coupled from the conference call bridge to the receive side attenuator, and logic which when executed is operable to cause the conference call bridge to determine the additional amount of attenuation to introduce and to provide the additional amount of attenuation to introduce to the receive side attenuator on the first control signal path.

7. The apparatus of claim 6, further comprising a second control signal path coupled from the double-talk detector to the receive side attenuator, and logic which when executed is operable to cause the conference call bridge to communicate with the double-talk detector using one or more of the control signal paths to determine the level of echo canceled by the convolution processor.

8. The apparatus of claim 1, further comprising logic which when executed causes obtaining an echo return loss enhancement (ERLE) value from the convolution processor and using the ERLE to determine the additional amount of attenuation.

9. The apparatus of claim 1, further comprising logic which when executed causes activating the receive side attenuator only when a speaker engaged in double-talk is actually in a mix of speakers that are being played out from the conference call bridge.

10. A conference call bridge apparatus, comprising:

a mixer;

a plurality of echo cancellers coupled to the mixer, wherein each of the echo cancellers comprises;

a receive side attenuator coupled in a receive side signal path that is configured to couple from the mixer to a caller;

a convolution processor coupled to the receive side signal path at a pick-off point;

a double-talk detector coupled to the receive side signal path and to a sending side signal path that is configured to couple from the caller to the mixer;

logic coupled to the receive side attenuator which is configured to;

responsive to a double-talk condition detected by the double-talk detector;

determine a level of echo canceled by the convolution processor,

determine an additional amount of attenuation to introduce to a caller input signal, and

activate the receive side attenuator to introduce the additional attenuation to the caller input signal;

wherein the caller input signal is provided to a caller causing the double-talk condition.

11. The apparatus of claim 10, further comprising logic which when executed by the processor is operable to disable the receive side attenuator when the double-talk condition ends, to detect a further occurrence of double-talk, and in response thereto, to stops or slows the adaptation of the convolution processor, deactivate a non-linear processor that is coupled in the sending side signal path, and to again activate the receive side attenuator to introduce the additional attenuation.

12. The apparatus of claim 10, wherein the receive side attenuator is coupled in the receive side signal path before the convolution processor pick-off point.

13. The apparatus of claim 10, wherein the receive side attenuator is coupled in the receive side signal path after the convolution processor pick-off point.

14. The apparatus of claim 10, further comprising a first control signal path coupled from a signal processor in the conference call bridge to the receive side attenuator, and logic which when executed is operable to cause the signal processor to determine the additional amount of attenuation to introduce and to provide the additional amount of attenuation to introduce to the receive side attenuator on the first control signal path.

15. The apparatus of claim 14, further comprising a second control signal path coupled from the double-talk detector to the receive side attenuator, and logic which when executed is operable to cause the signal processor to communicate with the double-talk detector using one or more of the control signal paths to determine the level of echo canceled by the convolution processor.

16. The apparatus of claim 10, further comprising logic which when executed causes obtaining an echo return loss enhancement (ERLE) value from the convolution processor and using the ERLE to determine the additional amount of attenuation.

17. The apparatus of claim 10, further comprising logic which when executed causes activating the receive side attenuator only when a speaker engaged in double-talk is actually in a mix of speakers that are being played out from the mixer.

18. A computer-implemented method, comprising:

in response to detecting an occurrence of double-talk in a call;

determining a level of residual echo that has been canceled by a convolution processor;

determining an amount of additional attenuation for a caller input signal to introduce in an echo canceller that is processing the call; and

activating a receive-side attenuator in the echo canceller to introduce the additional attenuation to the caller input signal;

wherein the caller input signal is provided to a caller causing the double-talk condition;

disabling the receive-side attenuator when the double-talk ends.

19. The method of claim 18, further comprising detecting a further occurrence of double-talk, and in response thereto, stopping or slowing the rate of adaptation of the convolution processor, deactivating a non-linear processor that is coupled in the sending side signal path, and again activating the receive side attenuator to introduce the additional attenuation.

20. The method of claim 18, further comprising activating the receive side attenuator in a receive side signal path, which is configured to couple from a conference call bridge to a caller, before a pick-off point in the receive side signal path at which a convolution processor is coupled.

21. The method of claim 18, further comprising activating the receive side attenuator in a receive side signal path, which is configured to couple from a conference call bridge to a caller, after a pick-off point in the receive side signal path at which a convolution processor is coupled.

22. The method of claim 18, further comprising activating the receive side attenuator in a conference call bridge.

23. The method of claim 18, further comprising determining in a conference call bridge the additional amount of attenuation to introduce and providing the additional amount of attenuation to introduce to the receive side attenuator on a first control signal path that is coupled from the conference call bridge to the receive side attenuator.

24. The method of claim 23, further comprising causing the conference call bridge to communicate with the double-talk detector to determine the level of echo canceled by the convolution processor, using one or more of the first control signal path and a second control signal path coupled from the double-talk detector to the receive side attenuator.

25. The method of claim 18, further comprising obtaining an echo return loss enhancement (ERLE) value from the convolution processor and using the ERLE to determine the additional amount of attenuation.

26. The method of claim 18, further comprising activating the receive side attenuator only when a speaker engaged in double-talk is actually in a mix of speakers that are being played out from the conference call bridge.