Downmix Loudness Adjustment for Consistent Multi-Device Audio
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Solution Overview
Problem
Consumer devices struggle to consistently reproduce high-quality, wide bandwidth audio content across varying media formats and playback environments due to limitations in dynamic range control and loudness consistency.
Innovation Solution
An audio processing system that includes an encoder and decoder capable of dynamic range control, using dynamic range compression curves, auditory scene analysis, and gain smoothing to adapt audio signals to specific playback environments, ensuring consistent loudness and spatial balance across different speaker configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dynamic range control processing is applied to audio content, then loudness consistency across different playback environments is improved, but the processing becomes irreversible and locks the decoder into specific assumptions about the playback environment
Solution Approach 1:
The patent segments the audio processing into two distinct parts: downmix processing (which is irreversible) and loudness adjustment processing (which remains reversible). By separating these functions, the system can apply dynamic range control to achieve loudness consistency while preserving the ability to adjust loudness later without being locked into irreversible assumptions about the playback environment.
Solution Approach 2:
The patent implements dynamic loudness adjustment that can adapt to different playback environments in real-time. The system calculates reference loudness levels and applies appropriate gain adjustments based on the actual playback conditions, allowing the audio output to dynamically adapt rather than being fixed by irreversible processing assumptions.
2Adaptability or versatility
If downmix processing is performed from multi-channel to stereo, then compatibility with stereo playback devices is improved, but loudness levels become inconsistent across different content types
Solution Approach 1:
The patent employs feedback mechanisms where the system measures the actual loudness of the downmixed audio content and uses this information to calculate appropriate gain adjustments. By measuring the reference loudness level and comparing it to target levels, the system can apply corrective gain adjustments to achieve consistent loudness across different content types while maintaining stereo compatibility.
Solution Approach 2:
The patent changes the loudness parameter of the downmixed audio content by applying calculated gain adjustments. The system modifies the loudness parameter dynamically based on the measured reference loudness level, ensuring that audio content maintains consistent perceived loudness across different content types and playback environments without compromising stereo compatibility.
Data Source
AI summary
Audio content coded for a reference speaker configuration is downmixed to downmix audio content coded for a specific speaker configuration. One or more gain adjustments are performed on individual portions of the downmix audio content coded for the specific speaker configuration. Loudness measurements are then performed on the individual portions of the downmix audio content. An audio signal that comprises the audio content coded for the reference speaker configuration and downmix loudness metadata is generated. The downmix loudness metadata is created based at least in part on the loudness measurements on the individual portions of the downmix audio content.