Echo Path Change Detection for Adaptive Filter Control
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Solution Overview
Problem
Existing echo cancellers in telephony struggle to adapt effectively to changes in the acoustic environment, often freezing adaptation during near-end speech, which can lead to inadequate echo cancellation and distortion.
Innovation Solution
An echo path monitoring system that generates a parameter indicative of the microphone signal's state, allowing the adaptive filter to operate in different modes based on the presence of near-end speech and echo path changes, including re-initializing adaptation parameters for quick convergence during echo path changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the adaptive filter is frozen during near-end speech to prevent divergence, then the filter stability is improved, but the echo cancellation accuracy deteriorates when echo path changes occur
Solution Approach 1:
The patent implements dynamic control of the adaptive filter by switching between frozen and adapting modes based on real-time detection of near-end speech and echo path changes. The controller monitors the microphone signal and automatically adjusts the filter's operation mode, allowing the system to transition from a static frozen state to a dynamic adapting state when echo path changes are detected, thereby resolving the contradiction between stability and accuracy.
Solution Approach 2:
The patent employs feedback mechanisms through the controller that continuously monitors the microphone signal for indicators of near-end speech and echo path changes. Based on this feedback, the controller adjusts the adaptive filter's operation mode, creating a closed-loop system that can automatically respond to changing conditions and maintain both stability during speech and accuracy during echo path changes.
2Measurement precision
If the adaptive filter operates in a steady state with continuous adaptation, then the echo cancellation is optimized, but the system responsiveness to echo path changes deteriorates
Solution Approach 1:
The patent creates a dynamic adaptation mechanism where the filter operates in steady state with continuous adaptation during normal conditions, but quickly transitions to a different operating mode when echo path changes are detected. This dynamic switching allows the system to maintain optimized echo cancellation during steady state while achieving rapid responsiveness to changes through automatic mode transition.
Solution Approach 2:
The system continuously monitors the microphone signal for indicators of echo path changes, preparing to switch to rapid adaptation mode when changes are detected. This preliminary monitoring and preparation allows the system to respond quickly to echo path changes without delay, while maintaining steady-state optimization during normal operation.
3Device complexity
If the adaptive filter uses a fixed adaptation rate, then the implementation simplicity is improved, but the adaptability to varying acoustic environments deteriorates
Solution Approach 1:
The patent implements dynamic adaptation rate adjustment where the filter operates with a standard adaptation rate during steady state, but switches to a different adaptation rate when echo path changes are detected. This dynamic adjustment of the adaptation rate allows the system to maintain implementation simplicity during normal operation while achieving high adaptability to varying acoustic environments through automatic rate adjustment.
Solution Approach 2:
The patent changes the adaptation rate parameter of the adaptive filter based on the detected operating conditions. By adjusting this key parameter dynamically between different rates depending on whether the system is in steady state or experiencing echo path changes, the system achieves versatility in handling different acoustic environments while keeping the base implementation simple.
Data Source
AI summary
An echo path monitoring system for controlling an adaptive filter configured to estimate an echo of a far-end signal comprised in a microphone signal, the system comprising a comparison generator configured to compare the microphone signal with the estimated echo to obtain a first comparison and compare an error signal, which represents a difference between the microphone signal and the estimated echo, with the estimated echo to obtain a second comparison, and a controller configured to combine the first and second comparisons to form a parameter indicative of a state of the microphone signal and, in dependence on said parameter, control an operating mode of the adaptive filter.