Spatial Distortion Removal Filter for Stereo Audio
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Solution Overview
Problem
2-channel stereo systems struggle to provide immersive audio experiences due to spatial distortion when transmitting sound images intended for lateral and rear positions, as they are reproduced through the front stereo system, leading to a lack of overall spatial sensation.
Innovation Solution
An audio signal processing device that filters 2-channel stereo signals using a spatial distortion removal filter, which includes ipsilateral and contralateral filters, to offset distortion during transmission, with threshold values adjusted based on frequency bands and channel responses to maintain signal stability and prevent excessive tonal changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a 2-channel stereo system is used for audio reproduction, then the sound image localization effect in the front direction is improved, but the overall spatial sensation and immersion are worsened because sound images intended for lateral and rear positions are reproduced through the front stereo system
Solution Approach 1:
The patent applies spatial distortion removal filters that modify frequency response parameters to compensate for the distortion caused by front stereo reproduction of lateral and rear sound images. The filter changes the amplitude and phase parameters of different frequency components to restore the intended spatial characteristics.
Solution Approach 2:
The patent replaces the need for physical surround speakers with a signal processing approach. Instead of using multiple speakers mechanically positioned around the listener, it uses digital filtering to simulate the spatial effect, substituting a mechanical acoustic system with an electronic signal processing system.
2Device complexity
If a 2-channel stereo system reproduces binaural signals, then the audio output is simplified, but the immersive audio experience is worsened due to signal distortion during transmission from speaker to listener
Solution Approach 1:
The patent applies preliminary anti-action by pre-compensating for the expected distortion before signal transmission. The spatial distortion removal filter is designed to anticipate and counteract the distortion that will occur during playback, applying inverse filtering to pre-correct the signal characteristics.
Solution Approach 2:
The patent uses feedback by measuring the actual distortion characteristics of the playback system and incorporating this information into the filter design. The filter parameters are adjusted based on measured distortion data, creating a closed-loop system that continuously optimizes signal accuracy.
3Adaptability or versatility
If spatial distortion removal filtering is applied across all frequency bands, then the spatial audio sensation is improved, but excessive tonal changes and signal instability occur
Solution Approach 1:
The patent applies local quality by differentiating the filtering approach across different frequency bands. Instead of applying uniform filtering, it applies spatial distortion removal filtering selectively to specific frequency ranges where distortion is most problematic, while leaving other bands less processed to maintain stability.
Solution Approach 2:
The patent uses partial action by applying filtering only to the extent necessary to remove spatial distortion without over-filtering. The filter strength and bandwidth are carefully controlled to achieve just enough distortion removal while avoiding the excessive filtering that would cause tonal changes and instability.
Data Source
AI summary
Disclosed is an audio signal processing device. The audio signal processing device includes a receiving end configured to receive a 2-channel stereo signal and a processor configured to process the 2-channel stereo signal. The processor is configured to filter the 2-channel stereo signal using a spatial distortion removal filter and output the filtered 2-channel stereo signal to a speaker including two or more channels. The spatial distortion removal filter is a filter for offsetting distortion that occurs when the output signal is transmitted from the speaker to a listener, and includes an ipsilateral filter applied to an ipsilateral signal of the 2-channel audio signal and a contralateral filter applied to a contralateral signal of the 2-channel audio signal.