Filter Matrix C for Crosstalk-Free Virtual Surround Audio
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Solution Overview
Problem
Existing audio signal processing technologies face challenges in providing accurate crosstalk-free virtual surround sound due to the instability and error sensitivity of inverse filters used in crosstalk cancellation units, leading to coloration and incorrect spatial perception.
Innovation Solution
The approach involves determining a filter matrix C based on the acoustic transfer function (ATF) matrix H and a target ATF matrix VH, which defines virtual loudspeaker positions, allowing for accurate filtering and combination of audio signals without the need for a conventional binauralization stage, thereby reducing errors and enhancing sound quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If inverse filters are used for crosstalk cancellation, then crosstalk is reduced, but the system becomes unstable and sensitive to errors
Solution Approach 1:
Instead of inverting the acoustic transfer function matrix H to obtain the crosstalk cancellation filter (which causes instability), the patent applies the filter matrix C directly to create virtual surround sound. The filter is designed to produce the desired acoustic effect without requiring inversion of the potentially ill-conditioned ATF matrix, thus avoiding the stability problems inherent in traditional inverse filter approaches.
2Loss of energy
If regularization is applied to control gain, then dynamic range loss is reduced, but manufacturing precision deteriorates
Solution Approach 1:
The patent changes the approach from controlling gain through regularization (which degrades spatial accuracy) to directly designing the filter matrix C with target spatial characteristics. By parameterizing the filter design around desired virtual loudspeaker positions and acoustic transfer functions, the system achieves accurate spatial positioning without relying on regularization that compromises precision.
3Adaptability or versatility
If binauralization units are combined with crosstalk cancellation, then virtual surround sound is provided, but coloration and wrong spatial perception occur
Solution Approach 1:
The patent merges the crosstalk cancellation function with virtual surround sound creation into a single integrated filter matrix C. Instead of using separate binauralization units followed by crosstalk cancellation (which serializes errors), the unified approach directly computes the filter that simultaneously achieves both objectives, eliminating the error accumulation that occurs when multiple processing stages are combined.
4Object-affected harmful factors
If exact crosstalk cancellation is pursued, then crosstalk is eliminated, but the system becomes overly sensitive to small errors
Solution Approach 1:
The patent applies partial cancellation by designing the filter matrix C to achieve virtual surround sound with acceptable crosstalk reduction rather than exact cancellation. This partial approach avoids the extreme sensitivity to errors that would result from pursuing perfect crosstalk elimination, providing a practical solution that balances performance with robustness.
Data Source
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AI summary
The invention relates to an audio signal processing apparatus (100) comprising a determiner (101) being configured to determine a filter matrix C on the basis of an acoustic transfer function matrix H and a target acoustic transfer function matrix VH, wherein the acoustic transfer function matrix H comprises transfer functions of acoustic propagation paths between loudspeakers and a listener and the target acoustic transfer function matrix VH comprises target transfer functions of target acoustic propagation paths, wherein the target acoustic propagation paths are defined by a target arrangement of virtual loudspeaker positions relative to the listener, a filter (103) being configured to filter the input audio signal on the basis of the filter matrix C to obtain filtered input audio signals, and a combiner (105) being configured to combine the filtered input audio signals to obtain output audio signals.