Multi-Channel Acoustic Echo Cancellation via Signal De-correlation
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Solution Overview
Problem
Multi-channel acoustic echo cancellation systems face challenges in converging to real room transfer functions when inter-correlation exists between signals, leading to inadequate echo suppression.
Innovation Solution
The method involves up-mixing stereo audio signals into additional channels, de-correlating these signals, and using adaptive filters to generate an echo-compensated microphone signal, with a de-correlation controller adjusting the degree of de-correlation based on adaptive filter performance to ensure accurate modeling of room transfer functions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multi-channel acoustic echo cancellation is used with correlated signals from multiple loudspeakers, then the system can handle complex audio environments, but the adaptive filters cannot converge to the real room transfer functions due to signal inter-correlation
Solution Approach 1:
The patent segments the multi-channel signal processing into separate single-channel adaptive filtering operations by de-correlating the input signals. Each loudspeaker channel is processed independently through its own adaptive filter, preventing inter-channel correlation from interfering with convergence to the true room transfer functions.
Solution Approach 2:
The patent introduces a de-correlation processing stage as an intermediary between the multi-channel loudspeaker signals and the adaptive filters. This intermediary transforms the correlated multi-channel signals into de-correlated signals that can be properly processed by standard single-channel adaptive filtering algorithms.
2Device complexity
If adaptive filters process correlated signals from different loudspeakers, then the system structure remains simple, but the filters compensate wrong signals and fail to model the actual room impulse responses
Solution Approach 1:
The patent applies de-correlation processing as a preliminary action before the adaptive filtering stage. By pre-processing the signals to remove correlations between channels, the system ensures that subsequent adaptive filtering operates on independent signals, guaranteeing convergence to the correct room transfer functions.
3Ease of manufacture
If standard adaptive filtering is applied to multi-channel correlated signals, then the implementation is straightforward, but the echo suppression performance becomes inadequate
Solution Approach 1:
The patent extracts the correlation component from the multi-channel signals through de-correlation processing. By removing the correlated portion that causes interference, the system enables standard adaptive filters to work effectively on the de-correlated signals, thereby improving echo suppression performance without complicating the overall implementation.
Data Source
AI summary
Multi-channel audio signal processing includes receiving a left stereo audio signal from a first channel and a right stereo audio signal from a second channel; up-mixing the left and the right stereo audio signals to generate an up-mixed audio signal for a third channel; de-correlating the up-mixed audio signal from the left and the right stereo audio signals to generate a de-correlated up-mixed audio signal; providing the left and right stereo signals and the de-correlated up-mixed audio signal to first, second, and third loudspeakers respectively to generate first, second, and third sound signals, respectively; picking up the first, second and third sound signals with a microphone to generate a microphone output signal; and adaptively filtering the microphone output signal with an acoustic echo canceller based on the left, the right, and the de-correlated up-mixed audio signal to generate an echo compensated microphone signal.