Systems and methods for acoustic echo cancellation

• US 8,208,621 B1
• Filed: 02/27/2008
• Issued: 06/26/2012
• Est. Priority Date: 10/12/2007
• Status: Active Grant

• Current Assignee: MediaTek, Inc.
• Original Assignee: MediaTek, Inc.
• Inventors: Hsu, Wei-Hao
• Primary Examiner(s): Jamal, Alexander
• Application Number:
  US12/038,162
• Time in Patent Office: 1,581 Days
• Field of Search: 379/406.05
• US Class Current: 379/406.05
• CPC Class Codes: H04M 9/082 using echo cancellers echo cancellers per se H04B3/23

Abstract

Acoustic echo cancellation methods are provided, in which first and second suppression gains of first and second sub-bands of an N^th acoustic frame are generated, and the second suppression gain of the second sub-band of the N^th acoustic frame is adjusted according to the first suppression gain of the first sub-band of the N^th acoustic frame.

Claims

1. An acoustic echo cancellation method, comprising:

generating a first suppression gain of a first sub-band of an N^th acoustic frame;

generating a second suppression gain of a second sub-band of the N^th acoustic frame; and

adjusting the second suppression gain of the second sub-band of the N^th acoustic frame according to the first suppression gain of the first sub-band of the N^th acoustic frame, wherein adjusting the second suppression gain of the Nth acoustic frame comprises;

detecting which determined range that a proportion of the second suppression gain of the Nth acoustic frame to the first suppression gain of which falls into;

determining an adjustment value according to the detected determined range; and

multiplying the second suppression gain of the second sub-band of the Nth acoustic frame by the determined adjustment value.

2. The acoustic echo cancellation method as claimed in claim 1, wherein the second suppression gain of the second sub-band of the N^th acoustic frame is adjusted when far end single talk or doubletalk occurs.

3. The acoustic echo cancellation method as claimed in claim 1, wherein the second suppression gain of the second sub-band of the N^th acoustic frame is adjusted when far end single talk or doubletalk occurs, and when a voice activity detection (VAD) value of far end acoustic signals of the second sub-band of the N^th acoustic frame does not exceed a first predetermined threshold.

4. The acoustic echo cancellation method as claimed in claim 1, wherein the first and second suppression gains of the first and second sub-bands of the N^th acoustic frame are generated according to a formula of

5. The acoustic echo cancellation method as claimed in claim 4, wherein the echo return loss value ERL_band is obtained by a formula of

6. The acoustic echo cancellation method as claimed in claim 1, further comprising:

updating an energy ratio of near end acoustic signals which have undergone a linear acoustic echo cancellation to far end acoustic signals of the second sub-band of an M^th acoustic frame by that of the N^th acoustic frame for adjusting the second suppression gain of the second sub-band of a K^th acoustic frame, when doubletalk does not occur, when a voice activity detection value of the second sub-band of the N^th acoustic frame exceeds a first predetermined threshold, and when a proportion of the first suppression gain of the first sub-band of the N^th acoustic frame to the second suppression gain of the second sub-band of which does not exceed a second predetermined threshold, wherein M<

N<

K.

7. An acoustic echo cancellation method, comprising:

generating a first suppression gain of a first sub-band of an N^th acoustic frame;

generating a second suppression gain of a second sub-band of the N^th acoustic frame; and

updating an energy ratio of near end acoustic signals which have undergone a linear acoustic echo cancellation to far end acoustic signals of the second sub-band of an M^th acoustic frame by that of the N^th acoustic frame for adjusting the second suppression gain of the second sub-band of a K^th acoustic frame, when doubletalk does not occur, when a voice activity detection value of the second sub-band of the N^th acoustic frame exceeds a first predetermined threshold, and when a proportion of the first suppression gain of the first sub-band of the N^th acoustic frame to the second suppression gain of the second sub-band of which does not exceed a second predetermined threshold, wherein M<

N<

K.

8. An acoustic echo cancellation system, comprising:

a nonlinear detection and adjustment unit comprising;

at least two preliminary suppression gain calculators generating first and second suppression gains of first and second sub-bands of an N^th acoustic frame; and

at least one nonlinear effect calculator adjusting the second suppression gain of the second sub-band of the N^th acoustic frame according to the first suppression gain of the first sub-band of the N^th acoustic frame with at least one adder

wherein the two preliminary suppression gain calculators generate the first and second suppression gains of first and second sub-bands of an N^th acoustic frame according to a formula of

9. The acoustic echo cancellation system as claimed in claim 8, further comprising a linear acoustic echo canceller performing a linear acoustic echo cancellation to near end acoustic signals of the first and second sub-bands of the N^th acoustic frame with one or more adders.

10. The acoustic echo cancellation system as claimed in claim 8, wherein the echo return loss value ERL_band is obtained by a formula of

11. The acoustic echo cancellation system as claimed in claim 8, wherein the nonlinear detection and adjustment unit further comprises a doubletalk detection unit detecting whether far end talk, near end talk or doubletalk occurs and outputting a detected result to the preliminary suppression gain calculators.

12. The acoustic echo cancellation method as claimed in claim 11, wherein the nonlinear detection and adjustment unit further detects a voice activity detection value of far end acoustic signals of the second sub-band of the N^th acoustic frame to adjust the second suppression gain of the second sub-band of which, when far end single talk or doubletalk occurs, and when the detected voice activity detection value does not exceed a first predetermined threshold.

13. The acoustic echo cancellation system as claimed in claim 8, further comprising a measure refresh unit updating an energy ratio of near end acoustic signals which have undergone a linear acoustic echo cancellation to far end acoustic signals of the second sub-band of an M^th acoustic frame stored in a register by that of the N^th acoustic frame, when doubletalk does not occur, when a voice activity detection value of the second sub-band of the N^th acoustic frame exceeds a first predetermined threshold, and when a proportion of the first suppression gain of the first sub-band of the N^th acoustic frame to the second suppression gain of the second sub-band of which does not exceed a second predetermined threshold, such that the suppression gain controller adjusts the second suppression gain of the second sub-band of a K^th acoustic frame, wherein M<

N<

K.

14. An acoustic echo cancellation system, comprising:

a nonlinear detection and adjustment unit generating first and second suppression gains of first and second sub-bands of an N^th acoustic frame; and

a measure refresh unit updating an energy ratio of near end acoustic signals which have undergone a linear acoustic echo cancellation to far end acoustic signals of the second sub-band of an M^th acoustic frame stored in a register by that of the N^th acoustic frame, when doubletalk does not occur, when a voice activity detection value of the second sub-band of the N^th acoustic frame exceeds a first predetermined threshold, and when a proportion of the first suppression gain of the first sub-band of the N^th acoustic frame to the second suppression gain of the second sub-band of which does not exceed a second predetermined threshold, such that the suppression gain controller adjusts the second suppression gain of the second sub-band of a K^th acoustic frame, wherein M<

N<

K.

15. The acoustic echo cancellation method as claimed in claim 14, wherein the nonlinear detection and adjustment unit comprises:

at least one nonlinear effect calculator detecting which determined range that a proportion of the second suppression gain of the N^th acoustic frame to the first suppression gain of which falls into, and determining an adjustment value according to the detected determined range; and

at least one multiplier multiplying the second suppression gain of the second sub-band of the N^th acoustic frame by the determined adjustment value.

16. The acoustic echo cancellation system as claimed in claim 15, wherein the nonlinear detection and adjustment unit further comprises a doubletalk detection unit detecting whether far end talk, near end talk or doubletalk occurs and outputting a detected result to the preliminary suppression gain calculators.

17. The acoustic echo cancellation method as claimed in claim 16, wherein the nonlinear detection and adjustment unit further detects a voice activity detection value of far end acoustic signals of the second sub-band of the N^th acoustic frame, and the nonlinear detection and adjustment unit adjusts the second suppression gain of the second sub-band of which when far end single talk or doubletalk occurs, and when the detected voice activity detection value does not exceed the first predetermined threshold.