Mid-Side Stereo Processing for Crosstalk Cancellation
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Solution Overview
Problem
Existing crosstalk cancelers face issues with ill-conditioning, leading to coloration and sensitivity to changes in the audio system, which affects the listening experience by requiring large drive signals and being prone to poor performance due to mismatches in Head Related Transfer Functions (HRTFs).
Innovation Solution
The system converts left-right stereo signals to mid-side stereo signals and applies filters only to the side-component, avoiding processing of the mid-component to reduce ill-conditioning effects, while generating virtual sound sources by controlling sound at each ear independently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If crosstalk cancellation is performed using traditional left-right stereo signal processing, then sound isolation at each ear is achieved, but the system suffers from ill-conditioning causing coloration and sensitivity to HRTF changes
Solution Approach 1:
The patent segments the stereo signal processing into two independent components: mid-component (M) representing the sum of left and right channels, and side-component (S) representing the difference. By separating the processing paths, the system applies crosstalk cancellation only to the side-component while leaving the mid-component unprocessed, thereby avoiding the ill-conditioning problems that affect traditional full-signal processing
Solution Approach 2:
The patent extracts and isolates the side-component signal (S = xL - xR) from the stereo signal pair, applying crosstalk cancellation processing specifically to this extracted component. The mid-component (M = xL + xR) is extracted and passed through without processing. This selective extraction and processing approach eliminates the coloration and sensitivity issues that plague traditional approaches that process the entire stereo signal
2Ease of operation
If filters are applied to both mid and side components for crosstalk cancellation, then virtual sound source generation is achieved, but ill-conditioning effects such as coloration increase
Solution Approach 1:
The patent applies different processing qualities to different signal components: the side-component receives full crosstalk cancellation filtering to achieve virtual sound source generation, while the mid-component receives no filtering processing. This local differentiation in processing quality allows the system to achieve the desired spatial audio effects while avoiding the application of filters that would cause coloration in the mid-component
3Reliability
If traditional crosstalk cancellation processing is applied, then sound isolation is achieved, but large drive signals are required and the system is sensitive to system changes
Solution Approach 1:
By segmenting the stereo signal into mid and side components and applying crosstalk cancellation only to the side-component, the system achieves sound isolation with reduced processing requirements. The mid-component passes through unprocessed, eliminating the need for large drive signals that would be required if filters were applied to both components, thereby reducing the power demand while maintaining isolation effectiveness
Data Source
AI summary
A system and method are described for transforming stereo signals into mid and side components xm and xs to apply processing to only the side-component xs and avoid processing the mid-component. By avoiding alteration to the mid-component XM, the system and method may reduce the effects of ill-conditioning, such as coloration that may be caused by processing a problematic mid-component xM while still performing crosstalk cancellation and/or generating virtual sound sources. Additional processing may be separately applied to the mid and side components xM and xs and/or particular frequency bands of the original stereo signals to further reduce ill-conditioning.