Spatial Audio Direction Quantization on a Spherical Grid
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Solution Overview
Problem
Current spatial audio encoding technologies are limited in effectively encoding and decoding sound-field parameters from various input types, including microphone-array captured signals, loudspeaker signals, and Ambisonic signals, particularly failing to accurately represent the spatial coherence of sounds in multi-channel formats like 5.1 or 7.1 mixes.
Innovation Solution
The proposed apparatus derives and rotates audio direction parameters based on elevation and azimuth values, quantizes differences, and indexes them using a spherical grid to efficiently encode and decode spatial audio signals, enabling accurate representation and synthesis of spatial audio across different input formats.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If audio direction parameters are directly encoded without rotation and repositioning, then the encoding process is simple, but the spatial coherence and accuracy of multi-channel audio formats deteriorate
Solution Approach 1:
The encoder performs preliminary rotation of the audio direction parameter set by the azimuth value of the first audio direction parameter, and preliminarily repositions parameters to match the spherical grid structure before quantization. This preliminary preparation enables accurate spatial representation while maintaining encoding efficiency.
Solution Approach 2:
The patent applies spherical grid geometry to organize audio direction parameters, mapping azimuth and elevation values onto a spherical coordinate system. This curved geometric structure naturally represents three-dimensional spatial relationships, improving spatial coherence accuracy for multi-channel audio formats.
2Measurement precision
If audio direction parameters are uniformly distributed on a spherical grid, then spatial representation accuracy improves, but the complexity of parameter transformation and quantization increases
Solution Approach 1:
The spherical grid structure serves multiple functions: it provides uniform angular distribution for accurate spatial representation, establishes a regular pattern for systematic quantization, and enables consistent mapping across different audio formats. This multi-functionality reduces overall system complexity despite the geometric transformation.
Solution Approach 2:
The patent transforms audio direction parameters from arbitrary coordinate systems to a standardized spherical grid parameter system with uniform angular spacing. This parameter standardization simplifies the quantization process and enables efficient encoding while maintaining high spatial representation accuracy.
3Productivity
If quantization is applied to audio direction parameters, then encoding efficiency improves, but the precision of spatial information is lost
Solution Approach 1:
The patent applies different quantization strategies to different components of the audio direction parameters. The rotated and repositioned parameters that align with the spherical grid are quantized with coarser steps, while the essential spatial relationships are preserved through the rotation operation. This localized differentiation of quality maintains spatial precision where critical while achieving compression where tolerant.
Data Source
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AI summary
There is disclosed inter alia an apparatus for spatial audio signal encoding configured to derive for each of a plurality of audio direction parameters a corresponding derived audio direction parameter comprising an elevation value and an azimuth value. Each derived audio direction parameter is rotated by the azimuth value of an audio direction parameter in the first position of the plurality of audio direction parameters. The position of some of the audio direction parameters are changed followed by determining for each of the plurality audio direction parameters a difference between each audio direction parameter and a corresponding rotated derived audio direction parameter. The difference for each of the plurality of audio direction parameters is then quantised.