Spatial Audio Gain Control for Head-Tracked Binaural Output
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Solution Overview
Problem
Conventional automatic gain control (AGC) and dynamic range compression algorithms introduce delay in audio systems, which is undesirable for head-tracking spatial audio applications, leading to suboptimal audio quality and increased headroom requirements due to variability in audio signal levels based on listener orientation.
Innovation Solution
A method that estimates the level of binaural output signals using head-tracking information and sound source positions, integrating gain control into the spatial audio processing system to apply smooth, frequency-dependent gains without introducing additional delay or processing load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional automatic gain control (AGC) and dynamic range compression algorithms are used to balance the loudness of the audio signal, then the loudness balance is improved, but the system introduces delay which deteriorates the perceived spatial-audio quality
Solution Approach 1:
The system pre-calculates and stores gain values in lookup tables based on possible head orientations and sound source positions. During runtime, the appropriate gain value is retrieved directly from the table based on the current head orientation and sound source position, eliminating the need for real-time delay-based processing while maintaining proper loudness balance.
2Reliability
If additional headroom is allocated to accommodate orientation variability in the audio signal, then clipping is avoided, but the headroom requirement increases which is not desired for portable players
Solution Approach 1:
The system pre-calculates maximum output levels for different head orientations and sound source positions during the lookup table generation phase. This allows the system to allocate minimal necessary headroom for each specific orientation scenario rather than allocating excessive headroom for all possible orientations, reducing overall headroom requirements while preventing clipping.
Solution Approach 2:
The system applies orientation-specific gain control where each head orientation has its own pre-calculated gain values in the lookup table. This allows the system to optimize headroom usage locally for each orientation rather than using a conservative global headroom allocation, reducing the total headroom requirement while maintaining clipping avoidance.
3Manufacturing precision
If head-tracking input is used to render binaural audio that moves with head movement, then spatial audio quality is improved, but the output level varies with orientation which requires additional processing complexity
Solution Approach 1:
The system pre-calculates and stores gain values for all possible head orientations and sound source positions in lookup tables during system initialization or calibration. During audio playback, the system simply queries the lookup table using the current head orientation and sound source position to retrieve the appropriate gain value, replacing complex real-time processing with simple table lookups and reducing processing complexity while maintaining spatial audio quality.
Data Source
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AI summary
Apparatus comprising a processor configured to: provide a position for at least one sound source relative to a reference position; analyse at least one input audio signal associated with the at least one sound source to determine at least one gain value based on the at least one input audio signal and the position for the at least one sound source relative to the reference position; and synthesize at least two output channels based on the at least one input audio signal, a directional transfer function pair, the at least one gain value and the position for the at least one sound source relative to the reference position.