Patent ID: 7366118

Claim:
A method of an echo canceller, which echo canceller includes a linear filter for generating an echo replica signal from filter coefficients of delay taps and an input signal to the filter, the method including the steps of: a) applying a signal transmitted in the direction of an echo source as input signal to a signal buffer, the signal buffer providing a delayed input signal to the input of the filter, which delayed signal has a delay that is subject to control by control logic included by the echo canceller, characterized by repeatedly performing the steps of: b) determining, based on a predetermined first mode switch condition, whether or not it should be attempted to increase the delay of the input signal to the filter, and if the first mode switch condition is met, entering an increase mode in which, if a ratio between a calculated measure based on a first set of filter coefficients and a calculated measure based on a second set of filter coefficients is below a first predetermined threshold, the buffer is controlled to increase the delay of the input signal; and c) determining, based on a predetermined second mode switch condition, whether or not it should be attempted to decrease the delay of the input signal to the filter, and if the second mode switch condition is met, entering a decrease mode in which, if a ratio between a calculated measure based on a third set of filter coefficients and the calculated measure based on the second set of filter coefficients is below a second predetermined threshold, the buffer is controlled to decrease the delay of the input signal.