Wideband Echo Cancellation Using Frequency-Dependent Processing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In wideband digital voice applications, existing echo cancellation techniques fail to effectively suppress high-band echo during double-talk conditions, leading to interference with direct voice signals, as they either attenuate both users' voices or fail to cancel high-band echo.
Innovation Solution
Implementing a high-frequency processor that is enabled during double-talk conditions to attenuate high-band echo, while allowing low-band echo to be canceled by a convolution processor, thereby preventing high-band echo from propagating and minimizing impact on direct voice signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a non-linear processor is enabled to attenuate high-band echo, then high-band echo is reduced, but during double-talk conditions it attenuates all signals including direct voice signals
Solution Approach 1:
The patent segments the frequency spectrum into low-band (0-4000 Hz) and high-band (4000-8000 Hz) components, applying different echo cancellation strategies to each. The convolution processor handles low-band echo while the high-frequency processor specifically targets high-band echo, allowing selective attenuation without affecting direct voice signals in either band during double-talk conditions.
Solution Approach 2:
The patent applies different processing characteristics to different frequency bands. The high-frequency processor is configured to attenuate only high-band echo signals while preserving direct voice signals through selective gain adjustment. The non-linear processor is selectively enabled or disabled based on the frequency band and talk condition, providing localized quality control.
2Object-affected harmful factors
If a convolution processor is used to cancel linear and time-invariant echo signals, then low-band echo is reduced, but it cannot cancel non-linear and time-variant high-band echo signals
Solution Approach 1:
The patent divides echo cancellation into two specialized processors: a convolution processor for linear and time-invariant low-band echo cancellation, and a high-frequency processor for non-linear and time-variant high-band echo cancellation. This segmentation allows each processor to be optimized for its specific frequency band and signal characteristics.
Solution Approach 2:
The high-frequency processor acts as an intermediary component that bridges the gap left by the convolution processor. It specifically handles the non-linear and time-variant high-band echo signals that the convolution processor cannot cancel, providing complementary functionality to achieve comprehensive echo cancellation across the entire wideband spectrum.
3Object-generated harmful factors
If the non-linear processor is disabled during double-talk to preserve direct voice signals, then voice transmission is maintained, but high-band echo is not attenuated
Solution Approach 1:
The patent segments the echo cancellation function into multiple specialized processors that can operate independently. During double-talk conditions, the convolution processor continues to cancel low-band echo while the high-frequency processor specifically targets high-band echo, allowing selective echo cancellation without disabling the entire non-linear processor and preserving direct voice signals.
Solution Approach 2:
The patent dynamically adjusts the operation of different processors based on talk conditions. During double-talk, the system maintains convolution processor operation for low-band cancellation while activating the high-frequency processor for high-band echo suppression. The non-linear processor is selectively enabled or disabled based on frequency band and talk condition, providing dynamic adaptation.
Data Source
AI summary
In one embodiment, an echo canceller configured to cancel echo in a wideband voice conference is provided. A double-talk condition may be when a plurality of users are speaking substantially simultaneously. When a double-talk condition is detected in the wideband conference, a high-frequency process is enabled and used to process signals in the high band to reduce echo. Accordingly, echo in the high band may not be produced by end devices being used by the users' speaking. Also, the users speaking have the echo cancelled in the low band and substantial echo does not result. This results in the users speaking experiencing the conference in the narrowband. The other users that are not speaking, however, continue to receive wideband signals. The users not speaking also continue to have echo cancellation performed for the high band and low band because these users are not speaking and thus attenuation of their voices is not a consideration.