Multichannel Loudness Scaling While Preserving Spatial Balance
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Solution Overview
Problem
Existing methods for adjusting the loudness of multichannel audio signals often disrupt the perceived spatial balance by applying a single gain to all channels, causing quieter channels to fall below the hearing threshold and altering the intended diffuse spatial balance.
Innovation Solution
Scaling the perceived loudness of each individual channel by a consistent amount while adjusting the gain of each channel to maintain the relative loudness between channels, optionally using a correction factor to minimize errors in overall loudness scaling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single gain is applied to all channels to adjust overall loudness, then the overall perceived loudness is scaled, but the perceived spatial balance is disrupted and quieter channels fall below the hearing threshold
Solution Approach 1:
The patent divides the audio signal into separate channels and processes each channel individually. By calculating and applying separate gains to each channel based on its specific loudness characteristics, the system maintains the relative loudness relationships between channels while achieving the desired overall loudness scaling, thus preserving spatial balance.
Solution Approach 2:
The patent applies different gain adjustments to different channels based on their individual loudness characteristics. Each channel receives a tailored gain value calculated from its specific loudness and the target loudness scaling factor, ensuring that quieter channels are boosted appropriately while louder channels are adjusted proportionally, maintaining the spatial distribution of sound sources.
2Productivity
If a single gain is applied to all channels, then the overall loudness is adjusted, but the relative perceived loudness between channels changes
Solution Approach 1:
The system segments the loudness adjustment process by calculating individual gains for each channel rather than applying a uniform gain. Each channel's gain is derived from its specific loudness measurement and the target scaling factor, ensuring that the relative loudness relationships between channels are preserved while achieving efficient overall loudness control.
Solution Approach 2:
The patent employs a feedback mechanism where the specific loudness of each channel is measured, compared against the target loudness scaling factor, and used to calculate the appropriate gain adjustment. This closed-loop approach ensures accurate relative loudness maintenance while achieving the desired overall loudness scaling.
3Reliability
If individual channel loudness is scaled independently, then spatial balance is preserved, but calculation complexity increases
Solution Approach 1:
The patent applies local quality by calculating specific gains for each channel based on its individual loudness characteristics. While this requires separate calculations for each channel, the process follows a consistent algorithmic approach that measures specific loudness, applies the target scaling factor, and determines the appropriate gain, making the complexity manageable and systematic.
Solution Approach 2:
The system changes the parameter being adjusted from a single overall gain to multiple channel-specific gains. Each gain value is derived by transforming the target loudness scaling factor through the specific loudness parameter of each channel, creating a systematic parameter transformation approach that preserves spatial balance while maintaining computational efficiency.
Data Source
AI summary
Scaling, by a desired amount sm, the overall perceived loudness Lm of a multichannel audio signal, wherein perceived loudness is a nonlinear function of signal power P, by scaling the perceived loudness of each individual channel Lc by an amount substantially equal to the desired amount of scaling of the overall perceived loudness of all channels sm subject to accuracy in calculations and the desired accuracy of the overall perceived loudness scaling sm. The perceived loudness of each individual channel may be scaled by changing the gain of each individual channel, wherein gain is a scaling of a channel's power. Optionally, in addition, the loudness scaling applied to each channel may be modified so as to reduce the difference between the actual overall loudness scaling and the desired amount of overall loudness scaling.