Adaptive echo canceller for voice messaging system
US5400394A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 23, 1994 |
| Grant date | Mar 21, 1995 |
| Priority date | — |
| Expiry date | Jun 23, 2014 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04Q1/45
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
An apparatus and method for echo cancellation in voice-messaging and voice-response systems, to enhance recognition of received DTMF and voice signals, comprising an efficient software echo canceller using adaptive digital filtering techniques. The voice messaging system includes analog telephone line interface modules which provide digitized voice data to a digital signal processor (DSP) chip. A transmit data line and a receive data line are each coupled to a cancel module with a cancel filter and an adapt/window module with an adaptive digital filter. The cancel filter causes echo cancellation on the receive data line; the adapt/window module monitors buffered transmit data in non-real time, without directly causing cancellation to occur, and selectively transfers an adjacent window of filter coefficients to the cancel filter under control of an adaptation control coupled to the adapt/window module. The control identifies a plurality of frames meeting a power criterion and passes the frames to the adaptive filter, which adapts on taps in frame segments during all available DSP real time, using a "cycle steal" approach for testing whether additional DSP processor cycles are availa…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.