Downmix Loudness Adjustment Across Changing Speaker Configurations
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Solution Overview
Problem
Consumer devices struggle to consistently reproduce high-quality, wide dynamic range audio content across varying media formats and playback environments due to limitations in dynamic range control and audio processing operations.
Innovation Solution
An audio encoder and decoder system that transmits dynamic range compression curves and auditory scene analysis parameters, allowing for customizable audio processing in real-time to maintain consistent loudness levels and spatial balance across different playback environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dynamic range compression is applied to audio content, then loudness consistency across different playback environments is improved, but device complexity increases due to the need for encoding and decoding processing operations
Solution Approach 1:
The audio encoder pre-calculates and embeds dynamic range compression metadata and compression curves into the audio bitstream before transmission. This preliminary action allows the decoder to apply pre-determined compression parameters without real-time calculation, reducing processing complexity while maintaining loudness consistency across different playback environments
Solution Approach 2:
The patent introduces an intermediary metadata structure that carries compression curves and processing parameters between encoder and decoder. This intermediary layer separates the complex compression algorithm development from the playback device implementation, allowing standardized processing without requiring full reproduction of the compression logic at the decoder
2Reliability
If audio content is encoded for reference speaker configuration, then spatial balance is improved, but adaptability to different playback configurations deteriorates
Solution Approach 1:
The patent encodes multiple sets of downmix parameters corresponding to different speaker configurations (e.g., 5.1, 7.1, stereo, mono) into the audio bitstream. The decoder selects and applies the appropriate parameter set based on the actual playback configuration, maintaining spatial balance by using reference configuration parameters while adapting to different physical setups through parameter substitution
Solution Approach 2:
The downmix parameter structure is designed to be universal across multiple speaker configurations. A single encoded parameter set can serve multiple playback scenarios by adjusting interpretation rather than requiring separate encoding for each configuration, enabling one audio stream to maintain spatial balance across diverse playback environments
3Device complexity
If downmix parameters are encoded without loudness offset compensation, then device complexity is reduced, but measurement precision of loudness levels deteriorates
Solution Approach 1:
The patent extracts loudness offset information as a separate compensatory parameter from the overall downmix process. Rather than incorporating offset calculations into the core downmix parameters, the offset is taken out as a distinct metadata element that adjusts the reference loudness level independently, maintaining simple downmix processing while achieving accurate loudness measurement through additive compensation
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.