Adaptive Smoothing for Inter-Channel Time Difference Estimation
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Solution Overview
Problem
Conventional stereo processing techniques, particularly in speech communications, face challenges in accurately determining inter-channel time differences, especially in scenarios with non-coincident microphones and varying audio sources, leading to suboptimal robustness and quality in recreating natural ambience and handling multiple speakers.
Innovation Solution
An apparatus and method that calculate a cross-correlation spectrum for two channel signals, estimate spectral characteristics, and apply smoothing filters based on these characteristics to enhance the accuracy of inter-channel time difference determination, combined with broadband and narrowband alignment parameters for optimal channel alignment and coding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional cross-correlation methods are used to estimate inter-channel time difference, then the estimation can be obtained, but the robustness and accuracy deteriorate in scenarios with non-coincident microphones and varying audio sources
Solution Approach 1:
The patent applies dynamics by making the smoothing filter adaptive rather than fixed. The filter's characteristics change dynamically based on the spectral characteristics of the input signal, allowing the system to automatically adjust to different audio scenarios such as speech, music, or environmental sounds, thereby improving both accuracy and robustness across varying conditions
Solution Approach 2:
The patent changes the parameters of the smoothing filter based on spectral characteristics of the signal. By analyzing spectral features and adjusting filter parameters accordingly, the system adapts to different audio content types and recording conditions, resolving the contradiction between maintaining high estimation accuracy and achieving robustness across diverse scenarios
2Reliability
If spectral smoothing is applied to improve estimation robustness, then the reliability improves, but the computational complexity increases
Solution Approach 1:
The patent applies local quality by selectively applying spectral smoothing only in frequency regions where it provides benefit. By analyzing spectral characteristics and applying smoothing adaptively in specific frequency bands rather than uniformly across the entire spectrum, the system achieves improved robustness while minimizing unnecessary computational overhead
3Loss of substance
If conventional parametric stereo is used for speech processing, then the bitrate is reduced, but the quality deteriorates for conversational scenarios with non-coincident microphones
Solution Approach 1:
The patent makes the stereo processing dynamic by using adaptive smoothing filters that adjust to the specific characteristics of speech signals recorded with non-coincident microphones. This dynamic adaptation preserves audio quality by accurately handling time differences while maintaining efficient parametric encoding for low bitrate transmission
Data Source
AI summary
An apparatus for estimating an inter-channel time difference between a first channel signal and a second channel signal, includes: a calculator for calculating a cross-correlation spectrum for a time block from the first channel signal in the time block and the second channel signal in the time block; a spectral characteristic estimator for estimating a characteristic of a spectrum of the first channel signal or the second channel signal for the time block; a smoothing filter for smoothing the cross-correlation spectrum over time using the spectral characteristic to obtain a smoothed cross-correlation spectrum; and a processor for processing the smoothed cross-correlation spectrum to obtain the inter-channel time difference.