Echo Delay Estimation via Frequency-Domain Cross-Correlation
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Solution Overview
Problem
Current echo delay time estimation methods in video conferencing are computationally complex and prone to errors due to environmental changes and equipment quality issues, leading to inaccurate echo suppression.
Innovation Solution
The proposed method involves a pre-processing device for time-to-frequency analysis, a dynamic vector calculating device for characteristic signal detection, and a cross-correlation calculating device to estimate echo delay time in the frequency domain, reducing computational complexity and improving accuracy by avoiding time-domain calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If time-domain cross-correlation calculation is used to estimate echo delay time, then the method is straightforward to implement, but the computational complexity increases and margins of error widen due to environmental changes
Solution Approach 1:
The patent transforms the signal from time domain to frequency domain by changing the parameter domain. This allows cross-correlation to be performed as element-wise multiplication in frequency domain, dramatically reducing computational complexity from O(N) to O(N log N) while improving accuracy by avoiding time-domain environmental interference
Solution Approach 2:
The patent replaces the mechanical time-domain cross-correlation calculation with a frequency-domain approach using Fast Fourier Transform. This substitution converts complex time-domain signal processing into simpler frequency-domain operations, reducing computational burden while maintaining or improving measurement precision
2Reliability
If adaptive filters (LMS or RLS) are used to suppress echo, then echo suppression performance improves, but the computational complexity increases significantly
Solution Approach 1:
The patent extracts only the essential characteristic - the echo delay time - from the complex adaptive filtering process. By using frequency-domain cross-correlation to directly obtain delay time, the system eliminates the need for computationally intensive LMS or RLS iterative filtering while achieving comparable echo suppression performance
Solution Approach 2:
Instead of using adaptive filters to iteratively suppress echo and then measuring delay, the patent inverts the approach by first measuring delay through frequency-domain cross-correlation and then using this information for echo suppression. This reversal eliminates the computational burden of adaptive filtering iterations
3Measurement precision
If testing impulse signal is broadcasted through speaker to measure acoustic impulse response, then echo delay can be measured, but equipment quality issues cause calculation errors
Solution Approach 1:
The patent uses a dynamic frequency sweep signal instead of a static impulse signal. The frequency sweep dynamically excites different frequency components of the speaker and acoustic environment, allowing the system to adapt to equipment limitations and identify the true echo delay by analyzing the dynamic response across multiple frequencies rather than relying on a single impulse measurement
Data Source
AI summary
Provided are an echo delay time estimation method and system thereof, wherein the echo delay time estimation method is executed by the echo delay time estimation system with the following steps: receiving a testing signal and a received signal and executing a time to frequency analysis to generate a testing signal spectrogram and a received signal spectrogram; respectively executing a characteristic signal dynamic detection calculation for the testing signal spectrogram and the received signal spectrogram to generate a testing signal characteristic dynamic vector and a received signal characteristic dynamic vector; executing a cross-correlated vector estimation for the testing signal characteristic dynamic vector and the received signal characteristic dynamic vector to generate a cross-correlated vector; and calculating an echo delay time according to the cross-correlated vector. The echo delay time estimation method is able to simplify calculations for estimating an echo delay time, alleviating some computational complexity.