Echo Cancellation Phase Correction Clock Drift
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Solution Overview
Problem
Conventional linear acoustic echo cancellation (LAEC) systems are sensitive to clock drifts between loudspeakers and microphones, leading to significant degradation in echo-return loss enhancement (ERLE) performance due to differences in sampling rates, causing acoustic echo signals to be out of sync.
Innovation Solution
Performing a phase correction operation on the echo signal estimate based on the clock drift between the microphone and loudspeaker signals, generating a real-valued filter using short-term Fourier transforms (STFTs) to align the phase of the echo signal with the microphone signal, and subtracting it to accurately estimate the captured message signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional linear acoustic echo cancellation (LAEC) is performed without phase correction, then the processing is simpler and faster, but the echo-return loss enhancement (ERLE) performance degrades significantly due to clock drift between loudspeaker and microphone sampling rates
Solution Approach 1:
The patent applies preliminary action by performing phase correction on the echo signal estimate before subtracting it from the microphone signal. The phase correction operation compensates for clock drift effects in advance, ensuring that the echo signal is properly aligned with the microphone signal before cancellation. This preliminary phase alignment prevents the degradation of ERLE performance that would otherwise occur due to sampling rate differences between the loudspeaker and microphone.
2Adaptability or versatility
If sampling rates of loudspeaker and microphone are kept identical, then clock drift is eliminated and echo cancellation is simpler, but the system loses adaptability to different audio device configurations and performance requirements
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the phase of the echo signal estimate based on the sampling rate difference between the loudspeaker and microphone. Instead of fixing the sampling rates to be identical, the system allows different sampling rates and compensates for the resulting phase misalignment through a phase correction operation. This correction factor is derived from the known sampling rate difference, enabling the system to adapt to various audio device configurations while maintaining precise echo signal alignment for effective cancellation.
Data Source
AI summary
Techniques of performing linear acoustic echo cancellation performing a phase correction operation on the estimate of the echo signal based on a clock drift between a capture of an input microphone signal and a playout of a loudspeaker signal. Along these lines, the existence of the clock drift, i.e., a small difference in the sampling rates of the input microphone signal and the loudspeaker signal, can cause processing circuitry in a device configured to perform LAEC operations to generate a filter based on the magnitudes of the short-term Fourier transforms (STFTs) of the input microphone signal and the loudspeaker signal. Such a filter is real-valued and results in a positive estimate of the acoustic echo signal included in the input microphone signal. The phase of this estimate may then be aligned with the phase of the input microphone signal.