Hierarchical Audio Dynamics Constraints for Spatially Stable Compression
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Solution Overview
Problem
Existing audio dynamics processing technologies face challenges in maintaining the spatial image and spectral balance when applying dynamic range control, particularly with severe modifications, leading to artifacts like cross-modulation and pumping, which alter the perceived sound unnatural and disturb listeners.
Innovation Solution
A hierarchical control path architecture is introduced, where information is passed down a control path hierarchy from top to bottom, imposing constraints on audio signal dynamics processing across multiple levels, including total, channel, and band levels, to manage signal modifications and prevent unwanted artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If dynamic range control is applied independently to each channel, then pumping artifacts are reduced, but the spatial image becomes unstable and virtual sources wander
Solution Approach 1:
The audio signal is divided into multiple frequency bands using a filter bank, and dynamic range control is applied independently to each band. This segmentation allows different compression parameters to be used for different frequency ranges, reducing pumping artifacts caused by uniform compression across all frequencies while maintaining spatial image stability through coordinated control of the segmented bands.
Solution Approach 2:
Different dynamic range control parameters are applied to different frequency bands based on their specific characteristics. Each band can have its own compression ratio, threshold, and attack/release times, allowing localized optimization that reduces pumping in problematic frequency ranges while preserving the overall spatial image through consistent control across bands.
2Stability of the object's composition
If severe dynamic range control modifications are applied, then signal level fluctuations are reduced, but cross-modulation artifacts and unnatural pumping effects increase
Solution Approach 1:
The system uses periodic analysis of the audio signal across different frequency bands to detect when pumping artifacts are occurring. Based on this periodic monitoring, the dynamic range control parameters are dynamically adjusted to reduce cross-modulation artifacts while maintaining signal level stability, preventing the unnatural pumping effects associated with severe compression.
3Stability of the object's composition
If total level measurement is used for multichannel audio, then spatial image is preserved, but channel-specific pumping artifacts occur
Solution Approach 1:
The system segments the multichannel audio signal into multiple frequency bands and applies separate level measurement and dynamic range control to each band. This allows the preservation of spatial image through overall level control while simultaneously preventing channel-specific pumping artifacts through band-specific compression management.
Solution Approach 2:
The patent introduces an intermediary control mechanism that coordinates between the total level measurement (for spatial image preservation) and individual channel/band measurements (for artifact prevention). This intermediary layer reconciles the conflicting requirements by distributing compression control across frequency bands while maintaining the overall spatial relationship between channels.
Data Source
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Figure 2a
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AI summary
Information useful for modifying the dynamics of an audio signal is derived from one or more devices or processes operating at one or more respective nodes of each of a plurality of hierarchy levels, each hierarchical level having one or more nodes, in which the one or more devices or processes operating at each hierarchical level takes a measure of one or more characteristics of the audio signal such that the one or more devices or processes operating at each successively lower hierarchical level takes a measure of one or more characteristics of progressively smaller subdivisions of the audio signal.