Frequency-Domain Latency Estimation for Audio Echo Cancellation

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Solution Overview

Problem

Echo cancellation systems face complexity and inefficiency when estimating time delay between audio signals, particularly when using long time-domain correlation filters or requiring adaptation of predictive filters, which hinders effective time-alignment and audio processing.

Innovation Solution

A method for estimating latency between audio signals in the frequency domain without adapting predictive filters, using a frequency transform representation and heuristic parameters to determine coarse and refined estimates of time delay, allowing for accurate time-alignment without the need for separate time-domain correlation filters.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If time-domain correlation filters are used for delay estimation, then measurement precision is improved, but device complexity increases

Engineering Contradiction:

Improvedelay estimation accuracyVSAvoidsystem complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces time-domain correlation filtering (mechanical signal processing) with frequency-domain spectral analysis. By transforming the delay estimation problem into the frequency domain using spectral representations and phase differences, the system achieves accurate delay measurement without requiring complex time-domain correlation filters, thus reducing overall system complexity while maintaining precision.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the domain parameter from time-domain to frequency-domain representation. By analyzing signals in the frequency domain using spectral representations and examining phase differences across frequency bins, the system achieves accurate delay estimation through a simpler mathematical approach compared to time-domain correlation, resolving the contradiction between precision and complexity.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If adaptive filter methods are used for delay estimation, then measurement precision is improved, but ease of operation deteriorates

Engineering Contradiction:

Improvedelay estimation accuracyVSAvoidoperational simplicity

Core Design Contradiction:

Measurement precisionVSEase of operation

Solution Approach 1:

The patent substitutes adaptive filter methods with a direct frequency-domain phase analysis approach. By calculating delay from phase differences in spectral representations without requiring iterative adaptation, the system maintains high measurement precision while dramatically simplifying operational complexity and eliminating the need for complex adaptive algorithms.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent extracts the essential delay information directly from phase differences in the frequency domain, separating the delay estimation function from the complex adaptive filtering process. This extraction approach achieves accurate delay measurement without requiring the full adaptive filter machinery, improving ease of operation while maintaining precision.

Inventive Principle:

Principle #2Taking out (Extraction)

3Measurement precision

If long time-domain correlation filters are used, then measurement precision is improved, but processing speed decreases

Engineering Contradiction:

Improvedelay estimation accuracyVSAvoidprocessing speed

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The patent replaces computationally intensive time-domain correlation with efficient frequency-domain spectral analysis. By using Fast Fourier Transforms and analyzing phase relationships in the frequency domain, the system achieves the same delay estimation accuracy with significantly reduced computational complexity and faster processing speed.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent transitions the delay estimation problem from the time dimension to the frequency dimension. By analyzing phase differences across frequency bins rather than correlating time signals, the system achieves accurate delay measurement with much lower computational requirements, improving processing speed while maintaining precision.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Data Source

PatentUS11437054B2Sample-accurate delay identification in a frequency domain

Publication Date: 2022.09.06 DOLBY LABORATORIES LICENSING CORP

AI summary

Systems, methods, and computer program products for frequency-domain estimation of latency between audio signals. In some embodiments, the estimation is performed on first blocks of data indicative of samples of a first audio signal and second blocks of data indicative of samples of a second audio signal, and includes determining a coarse latency estimate, including by determining gains which, when applied to some of the second blocks, determine estimates of one of the first blocks, and identifying one of the estimates as having a best spectral match to said one of the first blocks. A refined latency estimate is determined from the coarse estimate and some of the gains. Optionally, at least one metric indicative of confidence in the refined latency estimate is generated. Audio processing (e.g., echo cancellation) may be performed on the frequency-domain data, including by performing time alignment based on the refined latency estimate.