Audio Loudness Equalization Using Instantaneous Metadata
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Solution Overview
Problem
Conventional loudness equalization methods neglect the time-varying levels of spectral bands in audio content, leading to spectral distortions due to nonlinear loudness perception, and often require complex real-time processing with latency limitations.
Innovation Solution
A metadata-based loudness equalization scheme that uses instantaneous loudness values to control a time-varying filter, compensating for spectral distortions by adjusting the playback level, which can be seamlessly integrated into existing standards like MPEG-D DRC, allowing for reduced complexity and lower latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional loudness equalization is performed using adaptive filters that amplify low frequency range, then loudness perception is improved, but device complexity increases and latency increases
Solution Approach 1:
The patent pre-calculates and stores equalization filter coefficients at different playback levels during the encoding phase. During playback, the system simply retrieves and applies the pre-computed coefficients corresponding to the current playback level, eliminating the need for complex real-time adaptive filtering while maintaining loudness equalization quality.
Solution Approach 2:
The system dynamically selects appropriate equalization coefficients based on the current playback level metadata. Instead of using a fixed filter or complex adaptive filter, the system switches between pre-computed filter sets that correspond to different playback levels, providing dynamic adaptation with minimal computational complexity.
2Reliability
If conventional loudness equalization uses adaptive filters, then loudness perception is improved, but processing delay increases
Solution Approach 1:
The equalization filter coefficients are pre-computed and stored during encoding, eliminating the need for real-time adaptive filtering calculations during playback. This preliminary preparation reduces processing delay while maintaining equalization quality.
3Use of energy by moving object
If playback level is reduced, then energy consumption is reduced, but spectral distortions occur due to nonlinear loudness perception
Solution Approach 1:
The patent applies different equalization filter coefficients to different frequency ranges based on the playback level. At reduced playback levels, the system selectively amplifies low frequency components using pre-computed filters, compensating for the nonlinear loudness perception and maintaining spectral accuracy without increasing overall energy consumption.
Solution Approach 2:
The system changes the equalization parameters (filter coefficients) based on the playback level metadata. When playback level is reduced, the system automatically selects filter coefficients that compensate for the expected spectral imbalances, maintaining consistent perceived loudness across different playback levels.
Data Source
AI summary
Dynamic loudness equalization of received audio content in a playback system, using metadata that includes instantaneous loudness values for the audio content. A playback level is derived from a user volume setting of the playback system, and is compared with a mixing level that is assigned to the audio content. Parameters are computed, that define an equalization filter that is filtering the audio content before driving a speaker with the filtered audio content, based on the instantaneous loudness values and the comparing of the playback level with the assigned mixing level. Other embodiments are also described and claimed.