Echo cancellers and echo cancelling methods
AssigneeLectrosonics, Inc.
InventorFerenc Nagy
Life of this patent
Estimating the term…
Abstract
Methods and systems for updating the adaptive filter of an echo canceller. A method of updating the adaptive filter of an echo canceller in which an estimated echo is resolved from a received signal and then subtracted from an incoming echo-contaminated signal so as to produce a filtered output signal, includes: obtaining a corrected impulse response of an echo reconstruction filter (ERF); calculating specified decision measures usable to decide whether to prospectively apply the corrected ERF impulse response or a current ERF impulse response; determining whether application of the corrected ERF impulse response would result in improved echo cancellation; and updating the ERF to apply the corrected impulse response, when it is determined that the updating would result in a lower residual echo.
Claims11
A method of updating the adaptive filter of an echo canceller in which an estimated echo is resolved from a received signal and then subtracted from an incoming echo-contaminated signal so as to produce a filtered output signal, comprising:
- obtaining a corrected impulse response (hc) of an echo reconstruction filter (ERF) by
- calculating a record of an estimated echo (Ee) from the ERF using a current ERF impulse response he and a record of a reference signal X,
- resolving an estimate of the local signal plus noise Ven by subtracting the estimated echo Ee from a record of an input signal Yn,
- estimating a residual frequency response Hr with a record of Ve and X using spectral estimates of SX and SVe,X, and
- computing the corrected ERF impulse response (hc) based on the spectral estimates using the following equation:
- hc
- =
- he
- +
- IFFT
-
- (
- S
- ^
- Ve
- ,
- X
- S
- ^
- X
- )
- ;
- calculating specified decision measures usable to decide whether to prospectively apply the corrected ERF impulse response hc or a current ERF impulse response he to a reference signal (X), the decision measures being
- (i) a mutual information rate (infoVeX) of an estimate of the signal plus noise (Ve) and the reference signal (X),
- (ii) an estimated echo return loss enhancement (ERLEi) of the echo canceller, and
- (iii) a corrected echo return loss enhancement (ERLEc) of the echo canceller;
- determining whether application of the corrected ERF impulse response hc would result in improved echo cancellation by
- (i) comparing a mutual information rate of infoVeX to a specified threshold, and
- (ii) comparing the ERLEc to the ERLEi;
- and
- updating the ERF to apply the corrected impulse response hc, when it is determined that the updating would result in a lower residual echo (Er).
A method of updating an echo reconstruction filter (ERF) having changeable coefficients, comprising:
- calculating a corrected impulse response (hc) of an echo reconstruction filter (ERF) by
- calculating a record of an estimated echo (Ee) from the ERF using a current ERF impulse response he and a record of a reference signal X,
- resolving an estimate of the local signal plus noise Ven by subtracting the estimated echo Ee from a record of an input signal Yn,
- estimating a residual frequency response Hr with a record of Ve and X using spectral estimates of SX and SVe,X, and
- computing the corrected ERF impulse response (hc) based on the spectral estimates using the following equation:
- hc
- =
- he
- +
- IFFT
-
- (
- S
- ^
- Ve
- ,
- X
- S
- ^
- X
- )
- ;
- calculating specified decision measures usable to decide whether to apply a current ERF or an updated ERF to echo-contaminated signals in the future;
- deciding, based on the calculated decision measures, whether the hc would have yielded a lower residual echo (Er) than the current impulse response of the ERF (he) when applied to past observations;
- and
- replacing the coefficients of the ERF so that an impulse response of the ERF (he) equals hc.
A method of updating the adaptive filter of an echo canceller in which an estimated echo is resolved from a received signal and then subtracted from an incoming echo-contaminated signal so as to produce a filtered output signal, comprising:
- obtaining a corrected impulse response (hc) of an echo reconstruction filter (ERF);
- calculating specified decision measures usable to decide whether to prospectively apply the corrected ERF impulse response hc or a current ERF impulse response he to the reference signal;
- determining whether application of the corrected ERF impulse response hc would result in improved echo cancellation;
- and
- updating the ERF to apply the corrected impulse response hc, when it is determined that the updating would result in a lower residual echo (Er),
- wherein the obtaining includes
- calculating a record of an estimated echo (Ee) from the ERF using a current ERF impulse response he and a record of a reference signal X,
- resolving an estimate of the local signal plus noise Ven by subtracting the estimated echo Ee from a record of an input signal Yn,
- estimating a residual frequency response Hr with a record of Ve and X using spectral estimates of SX and SVe,X, and
- computing the corrected ERF impulse response (hc) based on the spectral estimates using the following equation:
- hc
- =
- he
- +
- IFFT
-
- (
- S
- ^
- Ve
- ,
- X
- S
- ^
- X
- )
- .
Dependencies are inferred from the claim text.