Spatial Audio Direction Quantization for Uniform Spherical Coverage
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Solution Overview
Problem
Conventional spatial audio encoding methods face challenges in uniformly distributing quantization and encoding states for directional components, leading to uneven distribution near the 'poles' of the direction sphere, particularly in multi-channel loudspeaker and Ambisonic inputs.
Innovation Solution
The proposed solution involves scalar quantization of elevation and azimuth components using a spherical grid, where distances between points on a unit sphere are calculated to select the optimal indexed values, ensuring a more uniform distribution of directions by limiting elevation quantization to adjacent indices and associating them with multiple azimuth values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If uniform quantization is applied to elevation and azimuth components separately, then quantization simplicity is improved, but direction distribution uniformity deteriorates (higher density near poles)
Solution Approach 1:
The patent changes the quantization parameters by introducing a non-uniform azimuth step size that varies with elevation angle. The azimuth quantization step is made larger near the poles (high elevation angles) and smaller near the equator (low elevation angles), which compensates for the natural clustering of uniform quantization points near the poles and achieves more uniform directional coverage
Solution Approach 2:
The patent applies asymmetric quantization where the azimuth quantization is not uniform but depends on the elevation angle. This asymmetric approach creates different quantization densities in different regions of the spherical coordinate system, specifically reducing density near poles and increasing density near the equator to achieve overall uniform directional distribution
2Measurement precision
If more quantization states are used to improve direction accuracy, then measurement precision is improved, but data complexity increases
Solution Approach 1:
The patent optimizes the quantization parameters (number of elevation levels and azimuth steps) to achieve the required directional accuracy with minimal data. By using non-uniform azimuth steps adapted to elevation angles, the system achieves uniform directional coverage with fewer total quantization states compared to uniform quantization schemes
Data Source
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AI summary
There is disclosed inter alia an apparatus for spatial audio signal encoding which determines at least one spatial audio parameter comprising a direction parameter with an elevation component and an azimuth component. The elevation component and azimuth component of the direction parameter are then converted to an index value.