Audio Precompensation Filter for Spatially Robust Pre-Ringing Control
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Solution Overview
Problem
Current audio precompensation filters face challenges in achieving robust and perceptually acceptable sound reproduction, particularly in minimizing pre-ringings and post-ringings across different listening positions, as existing methods either fail to control pre-ringings effectively or introduce significant phase distortions.
Innovation Solution
A discrete-time audio precompensation filter design based on a Single-Input Multiple Output (SIMO) linear model that accounts for non-minimum phase zeros outside the stability region, using a product of inverse scalar magnitude responses and causal Finite Impulse Response (FIR) filters to limit pre-ringings to non-perceptible levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a precompensation filter is designed to minimize pre-ringings at a single listening position, then the sound quality at that position is improved, but the sound quality at other listening positions deteriorates due to lack of spatial robustness
Solution Approach 1:
The patent segments the filter design process by separately identifying and processing minimum phase zeros and non-minimum phase zeros. The overall precompensation filter is divided into two cascaded filters: a minimum phase filter handling zeros inside the unit circle, and a non-causal filter handling zeros outside the unit circle. This segmentation allows each filter to be optimized for its specific zero type while maintaining spatial robustness across multiple listening positions.
Solution Approach 2:
The patent extends the design from a single listening position to multiple listening positions by incorporating spatial robustness considerations. The filter design evaluates performance across p different listening positions, transforming the problem from a one-point optimization to a multi-point spatial optimization, thereby achieving adaptability across different spatial locations.
2Device complexity
If a minimum phase precompensation filter is used, then the filter design is simpler and stable, but pre-ringings cannot be effectively controlled and sound quality deteriorates
Solution Approach 1:
The patent segments the filter design process by separately identifying and processing minimum phase zeros and non-minimum phase zeros. The overall precompensation filter is divided into two cascaded filters: a minimum phase filter handling zeros inside the unit circle, and a non-causal filter handling zeros outside the unit circle. This segmentation allows each filter to be optimized for its specific zero type while maintaining spatial robustness across multiple listening positions.
Solution Approach 2:
The patent changes the approach by incorporating non-causal filtering to handle non-minimum phase zeros. Instead of being constrained to purely minimum phase filters, the design allows non-causal operations for the non-minimum phase component, fundamentally changing the filter parameters and structure to achieve better time-domain precision while controlling pre-ringings.
3Measurement precision
If non-causal filtering is applied to handle non-minimum phase zeros, then pre-ringings are controlled effectively, but the filter becomes more complex and implementation difficulty increases
Solution Approach 1:
The patent segments the filter design process by separately identifying and processing minimum phase zeros and non-minimum phase zeros. The overall precompensation filter is divided into two cascaded filters: a minimum phase filter handling zeros inside the unit circle, and a non-causal filter handling zeros outside the unit circle. This segmentation allows each filter to be optimized for its specific zero type while maintaining spatial robustness across multiple listening positions.
Solution Approach 2:
The patent introduces an intermediary approach by using a non-causal filter specifically for non-minimum phase zeros. This intermediary filter component bridges the gap between the minimum phase filter and the final output, handling the problematic non-minimum phase zeros that would otherwise cause severe pre-ringings, while the minimum phase filter handles the stable components.
4Measurement precision
If the precompensation filter is optimized for one listening position, then the sound reproduction accuracy at that position is improved, but the phase response and amplitude response deviate at other positions
Solution Approach 1:
The patent extends the design from a single listening position to multiple listening positions by incorporating spatial robustness considerations. The filter design evaluates performance across p different listening positions, transforming the problem from a one-point optimization to a multi-point spatial optimization, thereby achieving adaptability across different spatial locations.
Solution Approach 2:
The patent creates a universal precompensation filter that functions effectively across multiple listening positions. By designing the filter to minimize the sum of squared errors across p different positions and to work with both minimum phase and non-minimum phase zeros, the filter achieves multi-functionality, serving as a robust solution for spatially distributed listening positions rather than being optimized for a single point.
Data Source
AI summary
A discrete-time audio precompensation filter is designed based on a linear model that describes the dynamic response of a sound generating system at p>1 listening positions. The filter construction is based on providing information representative of n non-minimum phase zeros {Zi} that are outside of the stability region |z|=1 in the complex frequency domain. A causal Finite Impulse Response (FIR) filter, of user-specified degree d, having coefficients corresponding to a causal part of a delayed non-causal impulse response is determined based on the information representative of n non minimum phase zeros. The resulting precompensation filter is determined as the product of at least two scalar dynamic systems, represented by an inverse of a characteristic scalar magnitude response in the frequency domain representing the power gains at the listening positions, and the causal FIR filter designed to approximately invert only non-minimum phase zeros that are safely inverted.