Audio Loudness Metadata for Dynamic Range and Clipping Control
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Solution Overview
Problem
The varying dynamic range and loudness levels of digital audio signals across different end-user devices and playback environments lead to inconsistent user experiences, as existing technologies lack effective dynamic range control and loudness normalization methods.
Innovation Solution
The method involves applying an audio normalization gain value to an audio signal, computing dynamic range control (DRC) gain values based on predefined characteristics, and embedding these values as metadata with the encoded signal. During playback, the DRC gain values are adjusted using local parameters and user inputs to dynamically control the loudness and prevent clipping.
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 peak levels must be reduced to avoid clipping which reduces dynamic range
Solution Approach 1:
The patent applies dynamic range control during the encoding stage before delivery, pre-compressing the audio signal to prevent clipping at the decoder. This preliminary action ensures that peak levels are controlled in advance, allowing the decoded signal to be played back without clipping distortion while maintaining consistent loudness across different playback environments.
2Adaptability or versatility
If different audio signals are delivered to various end-user devices, then device compatibility is improved, but loudness consistency deteriorates due to varying analog signal paths and acoustic environments
Solution Approach 1:
The patent performs loudness normalization and dynamic range control during encoding, embedding the processed signal with metadata containing DRC gain values. This preliminary processing ensures that the audio signal is pre-adjusted for consistent perceived loudness across different playback devices, compensating for variations in analog signal paths and acoustic environments before the signal reaches the end-user device.
Solution Approach 2:
The system uses metadata containing DRC gain values that are derived from analyzing the original audio signal's loudness characteristics. This feedback mechanism allows the decoder to apply appropriate gain adjustments based on the encoded signal's properties, ensuring consistent loudness reproduction across different playback environments without requiring real-time analysis at the decoder.
3Measurement precision
If per-frame loudness calculations are performed to achieve precise loudness control, then loudness normalization precision is improved, but computational complexity and processing time increase
Solution Approach 1:
The patent calculates DRC gain values during the encoding stage and embeds them as metadata with the encoded audio signal. This preliminary calculation transfers the computational burden to the encoding phase, allowing the decoder to simply apply the pre-computed gain values without performing complex per-frame loudness analysis. This approach achieves precise loudness normalization while minimizing processing complexity at the playback device.
Data Source
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.