Higher-Order Ambisonics Spatial-Domain Compression for Lower Data Rates
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Solution Overview
Problem
Existing methods for compressing higher-order Ambisonics (HOA) representations of audio scenes are inefficient and fail to effectively utilize psycho-acoustic phenomena, leading to high data rates and loss of spatial information.
Innovation Solution
Transform HOA coefficients into spatial domain signals representing plane waves from specific directions, apply perceptual encoding to these signals, and multiplex the results for efficient compression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If higher-order Ambisonics (HOA) representations are used to describe complex spatial audio scenes, then spatial accuracy and sound field description quality are improved, but data rate increases significantly
Solution Approach 1:
The patent segments the HOA signal processing into multiple stages: transforming HOA coefficients into spatial domain signals representing plane waves from specific directions, applying perceptual encoding to these spatial signals, and multiplexing the results. This segmentation allows efficient compression while maintaining spatial accuracy by processing the signal in a more compressible domain.
Solution Approach 2:
The patent changes the domain parameter from HOA coefficient space to spatial domain signals. By transforming the representation from mathematical coefficients to physical plane wave signals from specific directions, the patent enables more efficient compression while preserving the essential spatial information needed for accurate sound field reproduction.
2Ease of manufacture
If conventional compression techniques are applied to HOA coefficients, then implementation simplicity is maintained, but compression efficiency is poor and spatial information is lost
Solution Approach 1:
The patent introduces spatial domain signals as an intermediary representation between HOA coefficients and the final compressed output. These spatial signals representing plane waves from specific directions serve as a mediating domain that preserves spatial information while being more amenable to efficient perceptual encoding and compression than raw HOA coefficients.
3Quantity of substance
If perceptual encoding is applied directly to HOA coefficients, then data rate reduction is achieved, but spatial masking effects are not utilized and compression efficiency is limited
Solution Approach 1:
The patent changes the parameter domain from HOA coefficients to spatial domain signals before applying perceptual encoding. This parameter change enables the utilization of spatial masking effects, where sounds from different directions can mask each other, leading to significantly improved compression efficiency while maintaining perceptual quality.
Data Source
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AI summary
Representations of spatial audio scenes using higher-order Ambisonics (HOA) technology typically require a large number of coefficients per time instant. This data rate is too high for most practical applications that require real-time transmission of audio signals. According to the invention, the compression is carried out in spatial domain instead of HOA domain. The (N+1)2 input HOA coefficients are transformed into (N+1)2 equivalent signals in spatial domain, and the resulting (N+1)2 time-domain signals are input to a bank of parallel perceptual codecs. At decoder side, the individual spatial-domain signals are decoded, and the spatial-domain coefficients are transformed back into HOA domain in order to recover the original HOA representation.