Audio DRC Metadata for Consistent Loudness Without Clipping
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Solution Overview
Problem
The varying dynamic range and loudness perception across different end-user devices and audio programs lead to an inconsistent user experience during digital audio playback, as existing technologies fail to effectively normalize loudness and control dynamic range across diverse devices and content types.
Innovation Solution
A systematic approach is implemented using metadata-enhanced digital audio coding and decoding, where dynamic range control (DRC) gain values are computed and embedded per frame, allowing for normalization and dynamic range adjustment during playback, utilizing a DRC processor in both encoding and decoding stages to ensure consistent loudness levels across different devices and content types.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If dynamic range control is applied to increase average loudness, then the average loudness is improved, but the peak levels must be reduced which causes clipping and audible distortion
Solution Approach 1:
The patent applies preliminary dynamic range control during the encoding stage to pre-compress the audio signal's dynamic range before encoding. This preliminary action ensures that peak levels are controlled in advance, preventing clipping during playback while maintaining improved average loudness without requiring additional processing at decoding
2Adaptability or versatility
If different audio programs are encoded with varying dynamic ranges, then the creative flexibility is improved, but the playback consistency across different devices deteriorates
Solution Approach 1:
The patent embeds metadata parameters including DRC gain values and DRC characteristics indices that describe the dynamic range control applied to each audio program. These parameters are stored with the encoded audio and automatically applied during playback, allowing each program to maintain its creative dynamic range characteristics while ensuring consistent playback behavior across different devices through standardized parameter application
3Measurement precision
If per-frame DRC gain values are embedded in metadata, then the loudness normalization precision is improved, but the data rate increases
Solution Approach 1:
The patent embeds per-frame DRC gain values in metadata to provide precise loudness normalization control at the frame level. This partial action approach applies DRC processing selectively to individual frames rather than continuously, achieving high precision loudness normalization while minimizing the additional data rate overhead by only encoding necessary gain values for frames requiring adjustment
Data Source
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AI summary
An audio normalization gain value is applied to an audio signal to produce a normalized signal. The normalized signal is processed to compute dynamic range control (DRC) gain values in accordance with a selected one of several pre-defined DRC characteristics. The audio signal is encoded, and the DRC gain values are provided as metadata associated with the encoded audio signal. Several other embodiments are also described and claimed.