Mid-Side Dynamic Range Control for Spatial Audio Thresholding
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Solution Overview
Problem
Existing audio processing technologies face challenges in dynamically controlling the range of audio signals in a spatially-aware context, particularly in shifting artifacts of range control to different spatial locations without compromising sound quality.
Innovation Solution
The method involves converting audio signals from left-right space to mid-side space, applying gain factors to the mid and side components based on priority, and then converting back to left-right space to ensure that the peaks of the output channels remain below a threshold, effectively shifting artifacts by prioritizing gain reduction between mid and side components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gain factors are applied to left and right channels in left-right space to achieve range control, then the peak of each channel is below the threshold, but artifacts of range control appear in the spatial audio signal
Solution Approach 1:
The patent transforms the audio signal from left-right stereo space to mid-side space, applying range control in a different dimensional representation. By converting to mid-side components (mid = left + right, side = left - right), the system can apply gain factors that push artifacts into the side channel, which is less perceptible to listeners, while maintaining threshold compliance in the original left-right channels.
Solution Approach 2:
The patent applies different gain factors to different spatial components (mid and side) based on their priority. The side component, which contains spatial information and artifacts, receives different treatment than the mid component, which contains the main audio content. This local differentiation allows artifacts to be shifted to less perceptible locations while preserving overall sound quality.
2Reliability
If gain reduction is applied to control the audio signal, then the threshold is satisfied, but sound quality deteriorates due to artifact introduction
Solution Approach 1:
The mid-side transformation acts as an intermediary that decouples the threshold control function from the main audio content. By representing the signal in mid-side space, the system can independently control the side component (which contains artifacts) without directly affecting the mid component (which contains the primary audio information), thereby maintaining sound quality while achieving threshold compliance.
Solution Approach 2:
The patent converts the harmful artifacts of range control into a beneficial spatial distribution. Instead of uniformly applying gain reduction that degrades sound quality, the system uses the side channel as a repository for artifacts, transforming what would be harmful distortions into spatially-separated, less perceptible elements that do not compromise overall audio quality.
3Ease of operation
If uniform gain factors are applied to both channels, then threshold control is simple, but spatial artifacts cannot be shifted to different locations
Solution Approach 1:
The patent segments the stereo signal into mid and side components, allowing independent processing of each component. This segmentation enables the application of different gain factors to mid and side channels, providing the versatility to shift artifacts spatially while maintaining the simplicity of a systematic processing approach. The mid-side transformation itself provides a structured framework that simplifies the implementation of complex spatial control.
Data Source
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Figure 3A~3B
AI summary
An audio signal is limited in an audio coordinate system using gain factors applied in another audio coordinate system. A first component and a second component in a first audio coordinate system is generated from a third component and a fourth component of the audio signal in a second audio coordinate system. An amplitude threshold defining a maximum level for each of the third component and the fourth component is determined. One or more gain factors are applied to each of the third component and the fourth component to generate an adjusted third component and an adjusted fourth component, and a first output channel and a second output channel in the second audio coordinate system are generated from the adjusted third and fourth components. The first and second output channels are each limited below the amplitude threshold from application of the one or more gain factors.