Browse Prior Art Database

Method for noncancelling taps for the early detection of double-talk in voice-echo cancellers

IP.com Disclosure Number: IPCOM000018764D
Publication Date: 2003-Aug-06
Document File: 3 page(s) / 113K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for noncancelling taps for the early detection of double-talk in voice-echo cancellers. Benefits include improved performance and an improved development environment.

This text was extracted from a Microsoft Word document.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 55% of the total text.

Method for noncancelling taps for the early detection of double-talk in voice-echo cancellers

Disclosed is a method for noncancelling taps for the early detection of double-talk in voice-echo cancellers. Benefits include improved performance and an improved development environment.

General description

        � � � � � The disclosed method is a linear, finite impulse response (FIR) filter. It is a beta filter that works in cooperation with the main FIR filter to cancel an echo.
Advantages

        � � � � � The disclosed method provides advantages, including:

·        � � � Improved performance due to detecting the double-talk (DT) earlier than the conventional method

·        � � � Improved performance due to requiring less processor execution speed

·        � � � Improved development environment due to requiring a simple type of assembly code

Detailed description

        � � � � � A FIR is required for modeling 2-wire to/from 4-wire (analog-hybrid) conversion in voice echo-cancellation applications (see Figure 1). This filter may have as many as 1024 taps to provide coverage of all delays up to 128 msec, assuming a sampling rate of 8 KHz.        � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � �

        � � � � � The taps of the FIR filter used to model the impulse response (IR) of the analog-hybrid conversion has a one-to-one correspondence to the samples of that IR sampled uniformly at frequency 8 KHz (such as, 0.125 msec apart in time). The set of IRs specified in the G.168 ITU specification is a good representation of the actual hybrids in real-life. These IRs have a length (the number of values that are not zero) less than 80, corresponding to IRs with a duration of less than 20 msec.

        � � � � � Not all of 1024 taps of the FIR filter are not zero. Only those 80 contiguous taps corresponding to the 80 samples of the IR of the hybrid are not zero, depending on the bulk delay in the echo-path.

        � � � � � These taps of the FIR filter are adapted using any of the well-known stochastic gradient algorithms, such as least mean squared (LMS), normalized least mean squared (NLMS), affine projection (AP) or r...