Spatial Audio Direction Quantization With Uniform Spherical Indexing
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Solution Overview
Problem
Existing spatial audio encoding methods face challenges in uniformly quantizing and encoding directional components, leading to uneven distribution of quantization and encoding states, particularly near the 'poles' of the direction sphere, which affects the accuracy of spatial audio reproduction.
Innovation Solution
The method involves converting elevation and azimuth components of the direction parameter into index values using a spherical grid and codebook-based indexing, where distances between points on a unit sphere are calculated to select the optimal indexed values, ensuring a more uniform distribution of directions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If uniform quantization and encoding is applied to azimuth and elevation components separately, then the encoding scheme is simple and systematic, but the distribution of quantization states becomes uneven near the poles of the direction sphere
Solution Approach 1:
The patent transforms the independent quantization of azimuth and elevation into a unified spherical coordinate quantization approach. By treating the direction as a point on a sphere and using spherical coordinate systems, the method ensures uniform distribution of quantization states across the entire spherical surface, including near the poles, while maintaining systematic encoding through indexed representation of spherical coordinates.
Solution Approach 2:
The patent changes the quantization parameters from separate uniform grids for azimuth and elevation to a unified spherical coordinate system with appropriate indexing. This parameter transformation ensures that the quantization density remains consistent across different regions of the sphere, particularly resolving the pole region density issue while preserving encoding efficiency through indexed parameter representation.
2Ease of operation
If separate uniform indexing is used for elevation and azimuth, then the encoding structure is regular and easy to implement, but the spatial resolution becomes non-uniform with higher density near the poles
Solution Approach 1:
The patent applies spherical coordinate transformation to unify the quantization approach. By representing directions as points on a sphere and using spherical coordinate systems with proper indexing, the method achieves uniform spatial resolution across all regions including the poles, while maintaining regular encoding structure through indexed spherical coordinate representation.
Solution Approach 2:
The patent introduces asymmetric indexing strategies for spherical coordinates where the number of azimuth bins varies with elevation. This asymmetric approach compensates for the geometric distortion in spherical coordinates, ensuring uniform spatial resolution by having fewer azimuth bins at higher elevations (near poles) and more bins at lower elevations (near equator), while still maintaining systematic encoding.
Data Source
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.