Inter-channel Time Difference Determination Using Local Maxima
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Solution Overview
Problem
Existing methods for determining the inter-channel time difference (ICTD) in multi-channel audio signals face ambiguities, especially with tonal components, leading to unstable frame-by-frame parametric synthesis and energy loss during down-mixing, as conventional approaches rely on global maxima in cross-correlation functions which can be ambiguous and fail to precisely track ICTD in evolving audio environments.
Innovation Solution
A method that determines local maxima of the cross-correlation function for both positive and negative time-lags, selects candidates based on amplitude differences, and identifies the energy-dominant channel to extract the ICTD, reducing ambiguities and stabilizing the inter-channel time difference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If global maxima in cross-correlation functions are used to determine ICTD, then the method is simple to implement, but ambiguities arise especially with tonal components leading to unstable frame-by-frame parametric synthesis
Solution Approach 1:
The patent segments the cross-correlation function analysis by identifying multiple local maxima rather than relying on a single global maximum. This segmentation allows the system to evaluate several candidate time lags and select the most appropriate one, thereby reducing ambiguities especially with tonal components while maintaining implementation feasibility.
Solution Approach 2:
The patent changes the parameter selection criterion from a single global maximum to multiple local maxima with amplitude comparison. By introducing amplitude thresholds and selecting candidates based on relative amplitude differences, the method transforms the ambiguous single-point selection into a multi-candidate evaluation process, improving reliability without significantly increasing complexity.
2Productivity
If conventional ICTD determination methods are used, then processing is computationally efficient, but energy loss occurs during down-mixing due to ambiguous ICTD values
Solution Approach 1:
The patent performs preliminary action by identifying and evaluating multiple local maxima candidates before final ICTD selection. This preliminary evaluation of amplitude differences and candidate comparison prevents ambiguous ICTD values from being selected, thereby avoiding energy loss during subsequent down-mixing operations while maintaining computational efficiency.
Solution Approach 2:
The patent introduces feedback mechanisms by comparing amplitude differences of local maxima and using this information to select the most appropriate ICTD candidate. This feedback loop ensures that the selected ICTD value is reliable and consistent, preventing energy loss during down-mixing while keeping the computational process efficient.
3Device complexity
If global maxima are used for ICTD determination, then the algorithm is computationally simple, but precise tracking of sound source localization is failed in evolving audio environments
Solution Approach 1:
The patent applies dynamics by making the ICTD selection adaptive to evolving audio environments. Instead of a static global maximum selection, the system dynamically evaluates multiple local maxima and their amplitude relationships, allowing precise tracking of sound source localization as the audio scene changes while maintaining reasonable algorithmic complexity.
Solution Approach 2:
The patent adds another dimension to the analysis by considering both the magnitude and relative amplitude relationships of multiple local maxima. This dimensional expansion from single-point to multi-point analysis enables precise sound source localization tracking in evolving environments without prohibitively increasing algorithmic complexity.
Data Source
AI summary
Disclosed methods and apparatuses determine an inter-channel time difference of a multi-channel audio signal by determining a set of local maxima of a cross-correlation function involving at least two different channels of the multi-channel audio signal, for positive and negative time-lags and associating each local maximum with a corresponding time-lag. Local maximums for the positive and negative time-lags are selected from the set as respective positive and negative time-lag inter-channel correlation candidates. Processing also includes evaluating whether there is an energy-dominant channel, when the absolute value of a difference in amplitude between the inter-channel correlation candidates is smaller than a first threshold, and, when there is an energy-dominant-channel, identifying the sign of the inter-channel time difference and extracting a current value of the inter-channel time difference based on the time-lag corresponding to the positive or negative time-lag inter-channel correlation candidate.