Multi-Channel AEC Self-Calibration with Orthogonalized References
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Solution Overview
Problem
Existing multi-channel acoustic echo cancellation techniques face challenges in accurately decorrelating reference signals, leading to non-uniqueness issues that impair self-calibration and system identification in media playback systems.
Innovation Solution
Implementing a multi-channel adaptive filter matrix with orthogonalization transformation and singular value decomposition to decorrelate reference signals, followed by estimating driver channel responses in the time domain, and applying octave smoothing to condition these responses for effective self-calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing multi-channel acoustic echo cancellation techniques are used, then echo cancellation is achieved, but accurate decorrelation of reference signals is not achieved leading to non-uniqueness issues
Solution Approach 1:
The patent applies orthogonalization transformation to change the parameters of the reference signal matrix, converting it into an orthogonal basis. This transformation resolves the non-uniqueness issue by ensuring that the decorrelated reference signals provide sufficient information for accurate system identification and self-calibration, directly addressing the contradiction between echo cancellation and measurement precision.
Solution Approach 2:
The patent introduces an intermediary transformation process (orthogonalization transformation followed by singular value decomposition) that mediates between the raw reference signals and the final system identification. This intermediary step decorrelates the signals and eliminates non-uniqueness, enabling accurate self-calibration while maintaining echo cancellation functionality.
2Reliability
If reference signals are decorrelated using existing techniques, then echo cancellation improves, but self-calibration accuracy deteriorates due to non-uniqueness
Solution Approach 1:
The patent applies orthogonalization transformation to change the parameters of the reference signal matrix, converting it into an orthogonal basis. This transformation resolves the non-uniqueness issue by ensuring that the decorrelated reference signals provide sufficient information for accurate system identification and self-calibration, directly addressing the contradiction between echo cancellation and measurement precision.
Solution Approach 2:
The patent replaces the conventional mechanical correlation-based echo cancellation with a mathematical transformation approach (orthogonalization and SVD). This substitution enables simultaneous achievement of echo cancellation and accurate self-calibration by using transformed reference signals that are both decorrelated and non-uniqueness-free.
3Device complexity
If driver channel responses are estimated in frequency domain, then processing is simplified, but accuracy for self-calibration is reduced
Solution Approach 1:
The patent transitions the driver channel response estimation from the frequency domain to the time domain through inverse Fourier transformation. This dimensional change enables accurate capture of impulse response characteristics necessary for self-calibration, while the orthogonalization transformation maintains computational efficiency. The time-domain representation provides the precision needed for accurate system identification.
Data Source
AI summary
Examples described herein relate to calibration of audio playback devices in a media playback system using inputs derived from a multi-channel adaptive filter of an acoustic echo canceller. Example playback devices described herein may utilize one or more techniques for calibration, which may be implemented as various calibration procedures. In some implementations, an example playback device may implement a self-calibration procedure, which involves the playback device calibrating (or re-calibrating) itself during operation. Yet further, the playback device may estimate acoustic impulse responses from a multi-channel adaptive filter of an acoustic echo canceller to use as inputs to the self-calibration procedure.