US 5,687,229 A · Method for controlling echo canceling in an echo canceller

Abstract

A method for controlling echo canceling in an echo cancellation system using a state machine controller. A far-end speech signal transmitted through a communications channel may be passed through an echo channel to produce an echo signal. The echo signal is summed with a near-end speech signal and transmitted back to the far-end. An echo canceller rejects the echo signal by forming an estimate of the echo signal and subtracting the estimate from the sum of the near-end speech signal and the echo signal. The echo canceller includes a state machine which is configured into a predetermined state of a plurality of states depending on the presence near-end speech signal, far-end speech signal, or both near-end and far-end speech signals. Based on the predetermined state of the state machine, the controller in the state machine controls the update of coefficients of a plurality of adaptive filters. The adaptive filters filter the far-end signal to form the estimate of the echo signal, which is canceled from an output signal provided to an output speech channel at the far-end.

Claims32

Dependent claims

A method of controlling echo cancellation, comprising the steps of:

filtering a far-end speech signal with a plurality of adaptive filters:
determining if one or both of a near-end speech signal and a far-end speech signal are present based on a result of said step of filtering:
selecting one cancellation state from a plurality of predetermined states, based on said step of determining;
performing echo cancellation on said far-end speech signal to generate an echo cancellation signal based on said step of selecting;
and
outputting said echo cancellation signal.

3 more elements

A method for controlling echo cancellation in an echo canceller, said echo canceller having one cancellation state of a predetermined plurality of states based on the presence of near-end and far-end speech signals, said echo canceller for generating a residual signal for output based on said cancellation state, said residual signal generated by filtering a far-end speech signal with a first adaptive filter to form an echo estimate signal and subtracting said echo estimate signal from a combined echo and near-end speech signal to form said residual signal, said echo canceller also having a second adaptive filter for filtering said far-end speech signal to generate a state signal for determining the presence of said near-end and far-end speech signals, comprising the steps of:

from a silent state indicative of the absence of said near-end speech signal and said far-end speech signal, transitioning into a far-end speech state when said far-end speech signal is present, and while in said far-end speech state indicative of the presence of only said far-end speech signal, updating coefficients of said first adaptive filter and synthesizing a noise signal for output in place of said residual signal;
from said far-end speech state, transitioning into said silent state when said far-end speech signal is no longer present;
from said silent state, transitioning into a near-end speech state when said near-end speech signal is present, and while in said near-end speech state indicative of the presence of only said near-end speech signal, suspending update of said first and second adaptive filters and generating said residual signal for output;
and
from said silent state, transitioning into a doubletalk state when said near-end and far-end speech signals are both present, and while in said doubletalk state indicative of the presence of both said near-end and far-end speech signals, updating coefficients of said second adaptive filter and generating said residual signal for output.

2 more elements

Dependencies are inferred from the claim text.

Method for controlling echo canceling in an echo canceller

Life of this patent

Method for controlling echo canceling in an echo canceller

Life of this patent

Abstract

Claims32