Hierarchical Audio Dynamics Control for Pumping-Free 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 high compression ratios, leading to artifacts like cross-modulation and pumping, which can alter the perceived sound quality.
Innovation Solution
A hierarchical control path architecture is introduced, where information is passed down through levels (Total, Channels, Bands) to apply constraints on dynamics processing, ensuring consistent modification across channels and frequency bands, reducing pumping and preserving spatial and spectral balance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dynamic range control with high compression ratio is applied to all channels based on total level measure, then the overall signal level is controlled within desired limits, but pumping artifacts occur and spatial image stability deteriorates
Solution Approach 1:
The patent segments the control path into multiple hierarchical levels: total level control and per-channel control. The total level measure controls the overall signal, while individual channel level measures control each channel separately. This segmentation allows the system to maintain overall level control while preventing pumping artifacts caused by uniform attenuation across all channels.
Solution Approach 2:
The patent applies different control strategies to different parts of the audio signal. The total level control applies to the overall signal, while per-channel level controls apply locally to individual channels. This local quality approach ensures that channels with transient peaks (like dialog) can be controlled independently without causing pumping in other channels (like background music).
2Object-generated harmful factors
If dynamic range control is applied independently to each channel, then pumping artifacts are reduced, but spatial image stability deteriorates due to differential attenuation
Solution Approach 1:
The patent merges the total level control with per-channel level controls in a hierarchical structure. The total level measure provides a reference that constrains the per-channel controls, ensuring that while channels can be controlled independently to prevent pumping, their combined effect maintains spatial image stability. This merging of control levels resolves the contradiction between independent channel control and spatial stability.
3Stability of the object's composition
If a single level measure is used for all channels, then spatial image is preserved, but cross-channel pumping occurs with severe modifications
Solution Approach 1:
The patent segments the level measurement into total level measure and per-channel level measures. The total level measure maintains spatial image stability by providing a unified control reference, while the per-channel level measures prevent cross-channel pumping by allowing independent control of each channel based on its own characteristics.
4Reliability
If severe dynamic range control is applied to handle loud segments, then peak levels are reduced, but background music fluctuates unnaturally
Solution Approach 1:
The patent applies local quality control by using per-channel level measures to identify which channels contain transient loud segments (like dialog) versus channels with continuous background music. The control system then applies severe dynamic range control only to channels with transient peaks while maintaining more stable control for channels with continuous content, preventing unnatural fluctuation in background music.
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.