Method and system for detection of onset of near-end signal in an echo cancellation system
AssigneeHellosoft, Inc.
InventorM. Senthil Kumar
Life of this patent
Estimating the term…
Abstract
A method, a system and a computer program product for fast detection of the onset of a near-end signal is provided. An Acoustic Echo Canceller (AEC) attenuates an acoustic echo present in a tele-communication network. The AEC includes an adaptive filter that estimates the acoustic echo and generates an error signal. The error signal is the difference between the acoustic echo and the estimate of acoustic echo plus a near-end signal, if present. The method comprises computing an onset indicator parameter from the error signal and the estimate of acoustic echo. Several other parameters are subsequently calculated by using the onset indicator parameter, the error signal and the estimate of acoustic echo.
Claims19
A method for use in Acoustic Echo Cancellation comprising:
- indicating onset of a near end speech signal at a near end of a two-way communication channel, responsive to at least one of (1) detecting, at a near end, a time in which an angle between a microphone output signal and an estimate of acoustic echo present at the near end is greater than a first threshold, and (2) detecting that a average onset indicator parameter at time instant n is greater than an onset detection threshold parameter from a previous time instant, and that the average onset indicator parameter is greater than a second threshold, wherein
- the onset indicator parameter at a time instant n is computed from an error signal produced from the microphone output signal at time instant n, and the estimate of acoustic echo at the time instant n, and
- an average onset indicator parameter at time instant n is computed from the onset indicator parameter.
An acoustic echo canceller, comprising:
- an adaptive filter operable to generate an estimate (y(n)) of an acoustic echo (d(n)) in a microphone output signal;
- a Non Linear Processor (NLP) comprising a switched attenuator operable to generate an output (eout(n)) that is either (1) comfort noise during times when near end speech is undetected or (2) the microphone output signal minus the estimate (y(n)) of the acoustic echo (d(n)) during times when near end speech is detected;
- and
- a Near-end Signal Detector (NSD) coupled to indicate presence of near end speech to the NLP and to the adaptive filter, wherein an Echo Return Loss Enhancement (ERLE), calculated as
- ERLE
- =
- 10
-
-
- log
- 10
-
- E
-
- [
- d
- 2
-
- (
- n
- )
- ]
- E
-
- [
- r
- 2
-
- (
- n
- )
- ]
- ,
- drops less than ten Decibels during a time in which a near end speech signal is present in the microphone output signal, compared with ERLE in the absence of the near-end speech signal.
A method for detection of onset of a near-end speech signal at a near end of a two-way voice communication channel, comprising:
- detecting, at a near end, a time in near end speech is occurring, the detecting comprising one or more of detecting that an angle between a microphone output signal and an estimate of acoustic echo present at the near end is greater than a first threshold;
- and
- after indicating presence of the near end speech signal, delaying a determination that the near end speech signal has ended, until a value of an onset indicator parameter at a current time instant, determined from an error signal (e(n)=d(n)+x(n)−y(n), wherein d(n) is the acoustic echo, x(n) is the near-end speech signal and y(n) is the estimate of acoustic echo) is within a threshold of an average of values of the onset indicator parameter in previous time instants.
Dependencies are inferred from the claim text.