Centre Channel Audio Extraction from Stereo Signals
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Solution Overview
Problem
Existing audio processing technologies fail to produce high-quality centre channel audio signals, leading to a poor listening experience when virtualized, as they lack user control over the level of central audio sources, resulting in listener fatigue and limited surround feeling.
Innovation Solution
A method and apparatus for processing audio signals that extract a centre channel audio signal from stereo signals using frequency-dependent magnitude and phase differences, comparing these against user-specific interaural level and phase differences to accurately determine and amplify or attenuate central audio sources, allowing for customizable gain control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multichannel audio signals are matrix downmixed to stereo for playback on portable devices, then compatibility with existing playback devices is improved, but the original multi-channel content is no longer available in its component form
Solution Approach 1:
The patent extracts the centre channel signal from the downmixed stereo audio by analyzing frequency-dependent magnitude and phase differences between the left and right channels. This extraction allows the original centre channel information to be recovered despite the lossy downmixing process, enabling users to access specific channel content while maintaining compatibility with stereo playback devices.
2Ease of operation
If stereo widening and 3D audio applications are applied to provide spatial audio experience, then user spatial feeling is improved, but listener fatigue increases due to unnatural playback
Solution Approach 1:
The patent applies local quality by selectively processing different frequency components and spatial information. It analyzes frequency-dependent characteristics to identify and enhance centre channel sources while preserving surround information, creating a localized enhancement rather than a global transformation. This approach maintains natural sound characteristics while providing spatial audio benefits.
Solution Approach 2:
The system dynamically adjusts audio processing based on real-time analysis of the audio signal's frequency content and spatial characteristics. By continuously monitoring and adapting the extraction and virtualization parameters, the system maintains natural sound quality while providing immersive spatial experience, preventing listener fatigue through dynamic optimization.
3Ease of operation
If centre channel extraction is performed from downmixed stereo signals, then user control over central audio sources is improved, but extraction quality is poor leading to unnatural virtualization
Solution Approach 1:
The patent replaces traditional mechanical mixing approaches with signal processing techniques that analyze frequency-dependent magnitude and phase differences. Instead of relying on simple mixing ratios, the system uses spectral analysis and mathematical transformations to accurately separate centre channel sources from surround information, achieving high extraction quality while maintaining user control.
4Ease of operation
If virtualization is applied to extracted centre channel signals, then spatial audio experience is improved, but lack of user control over level causes poor audio experience
Solution Approach 1:
The system dynamically adjusts the virtualization parameters and gain control based on the extracted centre channel signal characteristics and user preferences. By continuously adapting the processing parameters, the system provides immersive spatial audio experience while maintaining flexible user control over the level and characteristics of central sources.
Data Source
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AI summary
An apparatus comprising at least one processor and at least one memory including computer program code. The at least one memory and the computer program code is configured to, with the at least one processor, cause the apparatus at least to perform filtering at least two audio signals to generate at least two groups of audio components per audio signal, determining a difference between the at least two audio signals for each group of audio components, and generating a further audio signal by selectively combining the at least two audio signals for each group of audio components dependent on the difference between the at least two audio signals for each group of audio components.