Adaptive Delay Estimation for VoIP Echo Cancellation
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Solution Overview
Problem
Echo cancellation in Voice Over IP (VOIP) and Voice Recognition (VR) systems is hindered by clock unsynchronization between microphone and speaker devices, leading to incomplete echo cancellation due to varying sampling frequencies.
Innovation Solution
A signal processing device comprising an echo estimation device, a captured signal buffer, and a delay estimation device that compensates echo and captured signals with adaptive delay adjustments, dividing delay into fractional and integer components to effectively cancel echoes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If different hardware devices (microphone and speaker) are used for capturing and rendering sound, then the system can perform basic echo cancellation, but clock unsynchronization occurs leading to varying sampling frequencies and incomplete echo cancellation
Solution Approach 1:
The patent applies dynamics by making the delay compensation value adaptive and time-varying. Instead of using a fixed delay compensation, the system continuously estimates the time delay between reference and captured signals and updates the compensation value dynamically to track changes in sampling frequency synchronization, thereby resolving the contradiction between reliability and measurement precision.
Solution Approach 2:
The patent changes the parameter of delay compensation from a static value to a dynamically estimated value. By continuously estimating the time delay parameter based on correlation analysis between signals and updating the compensation accordingly, the system adapts to sampling frequency variations, improving echo cancellation completeness while accounting for synchronization precision limitations.
2Adaptability or versatility
If the sampling frequency difference between microphone and speaker is treated as a time-varying factor, then the system can adapt to frequency changes, but it becomes difficult for AEC to respond in real time and echo cannot be completely cancelled
Solution Approach 1:
The patent applies preliminary action by estimating the time delay using a sliding window approach that processes recent signal segments. This allows the system to predict and compensate for sampling frequency variations before they significantly impact echo cancellation performance, balancing adaptability with real-time processing requirements.
Solution Approach 2:
The patent uses partial action by focusing the delay estimation on the most recent time window rather than processing the entire signal history. This selective approach to delay estimation provides sufficient adaptability to frequency changes while maintaining computational efficiency for real-time operation, achieving a practical balance between adaptability and processing speed.
3Reliability
If a delay estimation method is implemented to adaptively estimate time delay, then echo cancellation effectiveness is improved, but the device complexity increases
Solution Approach 1:
The patent applies self-service by implementing an autonomous delay estimation and compensation system that automatically adapts to sampling frequency variations without requiring manual intervention or complex external control mechanisms. The system estimates delays and adjusts compensation values independently, improving echo cancellation effectiveness while keeping the complexity self-contained and manageable.
Solution Approach 2:
The patent uses feedback by continuously monitoring the captured signal and reference signal to estimate time delay, then using this estimation to adjust the delay compensation value. This closed-loop feedback mechanism improves echo cancellation effectiveness systematically while maintaining reasonable complexity through iterative refinement rather than complex open-loop control.
Data Source
AI summary
A signal processing device includes an echo estimation device, a captured signal buffer device and a delay estimation device. The echo estimation device generates an echo estimation signal according to a reference signal and a set of reflection path simulation coefficients and compensates the echo estimation signal according to a first delay to generate a compensated echo estimation signal. The captured signal buffer device buffers a captured signal captured by microphone device and outputs the captured signal according to a second delay to generate a compensated captured signal. The delay estimation device estimates an amount of delay adjustment according to the compensated echo estimation signal and the compensated captured signal and updates the first delay or the second delay according to the amount of delay adjustment. A difference between an upper bound and a lower bound of the first delay is smaller than or equal to 1.