Time-Domain DRC Metadata for High-Resolution Audio Gain Control
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Solution Overview
Problem
Current audio codecs, such as USAC and AAC, lack effective Dynamic Range Control (DRC) capabilities, leading to issues like limited time resolution, aliasing distortions, and inability to apply DRC gain values in the time domain, which results in suboptimal audio playback and increased complexity.
Innovation Solution
A system and method for encoding and applying DRC gain values in the time domain, using metadata to represent compression gain samples and parameters for interpolation, allowing for faster gain updates and avoiding MDCT artifacts by applying gains after signal reconstruction, supporting multi-band DRC and reducing decoder complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If DRC is applied using traditional AAC tools, then dynamic range compression is achieved, but time resolution is limited and aliasing distortions occur
Solution Approach 1:
The patent replaces the traditional frequency-domain MDCT-based DRC mechanism with a time-domain implementation. By applying DRC gains directly in the time domain after signal reconstruction rather than through MDCT transformation, the system achieves higher time resolution and eliminates the aliasing distortions inherent in frequency-domain approaches.
2Productivity
If DRC gain values are applied in the frequency domain using MDCT, then compression is achieved, but MDCT artifacts are introduced
Solution Approach 1:
The patent substitutes the MDCT frequency-domain processing mechanism with a time-domain gain application approach. DRC gains are calculated and applied directly to the time-domain audio signal after reconstruction, bypassing the MDCT transformation entirely and thereby eliminating MDCT-related artifacts while maintaining compression efficiency.
3Adaptability or versatility
If existing codec DRC tools are used, then dynamic range control is provided, but decoder complexity increases
Solution Approach 1:
The patent extracts the DRC gain calculation and application process from the complex frequency-domain MDCT framework and implements it as a separate, simplified time-domain operation. By decoupling DRC from the MDCT processing chain and applying gains directly in the time domain, the system reduces decoder complexity while maintaining full DRC capability.
4Measurement precision
If high time resolution DRC is implemented, then accurate gain updates are achieved, but computational complexity increases
Solution Approach 1:
The patent replaces complex frequency-domain analysis and transformation operations with direct time-domain gain application. By working exclusively in the time domain where gain updates can be applied sample-by-sample or frame-by-frame without requiring MDCT transformation, the system achieves high time resolution with reduced computational complexity.
Data Source
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AI summary
A system for encoding and applying Dynamic Range Control/Compression (DRC) gain values to a piece of sound program content is described. In particular, a set of DRC gain values representing a DRC gain curve for the piece of content may be divided into frames corresponding to frames of the piece of content. A set of fields may be included with an audio signal representing the piece of content. The additional fields may represent the DRC gain values using linear or spline interpolation. The additional fields may include 1) an initial gain value for each DRC frame, 2) a set of slope values at particular points in the DRC curve, 3) a set of time delta values for each consecutive pair of slope values, and/or 4) one or more gain delta values representing changes of DRC gain values in the DRC gain curve between points of the slope values.