SYSTEMS AND METHODS FOR STEREO ECHO CANCELLATION
First Claim
1. A method of cancelling an echo comprising:
- generating a difference signal by subtracting a first far-end signal from a second far-end signal;
generating a first echo cancellation signal by applying a first adaptive filter to the first far-end signal;
generating a difference echo cancellation signal by applying a difference adaptive filter to the difference signal;
subtracting the first echo cancellation signal from a received signal;
subtracting the difference echo cancellation signal from the received signal;
updating the first adaptive filter at a first adaptation rate; and
updating the difference adaptive filter at a second adaptation rate, where the first adaptation rate is different from the second adaptation rate.
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Abstract
Acoustic echoes in communications systems are distracting and undesirable. Acoustic echoes occur in communications systems where sound produced by a speaker is picked up by a microphone in a communications system. In a stereo playback environment, echo cancellation techniques become more complicated. Echo cancellation can be performed by performing echo cancellation on a center signal, which is the sum of a left channel signal and the right channel signal, or left signal and a difference signal, which is the difference of the right channel signal and the left channel signal. The adaptation rates of the two echo cancellers meet certain constraints to prevent degeneracies in the echo cancellation system.
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Citations
32 Claims
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1. A method of cancelling an echo comprising:
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generating a difference signal by subtracting a first far-end signal from a second far-end signal; generating a first echo cancellation signal by applying a first adaptive filter to the first far-end signal; generating a difference echo cancellation signal by applying a difference adaptive filter to the difference signal; subtracting the first echo cancellation signal from a received signal; subtracting the difference echo cancellation signal from the received signal; updating the first adaptive filter at a first adaptation rate; and updating the difference adaptive filter at a second adaptation rate, where the first adaptation rate is different from the second adaptation rate. - View Dependent Claims (2, 3, 4, 5, 6)
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7. In a two-way communications system, a method of cancelling an echo comprising:
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generating a difference signal by subtracting a first far-end signal from a second far-end signal; generating a center signal by adding the first far-end signal to the second far-end signal; generating a center echo cancellation signal by applying a center adaptive filter to the center far-end signal; generating a difference echo cancellation signal by applying a difference adaptive filter to the difference signal; subtracting the center echo cancellation signal from a received signal; subtracting the difference echo cancellation signal from the received signal; updating the center adaptive filter at a first adaptation rate; and updating the difference adaptive filter at a second adaptation rate, where the first adaptation rate is different from the second adaptation rate. - View Dependent Claims (8, 9, 10, 11, 12)
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13. A stereo echo cancellation system comprising:
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a first signal subtractor operable to generate a difference signal by subtracting a first far-end signal from a second far-end signal; a first adaptive filter operable to generate a first echo estimate from the first far-end signal; a difference adaptive filter operable to generate a difference echo estimate from the difference signal; a second signal subtractor operable to subtract the first echo estimate from a received signal; a third signal subtractor operable to subtract the difference echo estimate from the received signal; and wherein the first adaptive filter has an adaptation rate different from an adaptation rate for the difference adaptive filter. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
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24. A stereo echo cancellation system comprising:
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a first signal subtractor operable to generate a difference signal by subtracting a first far-end signal from a second far-end signal; a mixer operable to generate a center signal by adding the first far-end signal to the second far-end signal; a center adaptive filter operable to generate a center echo estimate from the center signal; a difference adaptive filter operable to generate a difference echo estimate from the difference signal; a second signal subtractor operable to subtract the center echo estimate from a received signal; a third signal subtractor operable to subtract the difference echo estimate from the received signal; and wherein the center adaptive filter has an adaptation rate different from an adaptation rate for the difference adaptive filter. - View Dependent Claims (25, 26, 27, 28, 29, 30, 31, 32)
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Specification