HOA Background Channel Decorrelation for Audio Compression
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Solution Overview
Problem
Higher-order ambisonics (HOA) audio data processing faces challenges in reducing correlation between background signals, leading to noise unmasking and inefficient compression, particularly in decoding and rendering across varying speaker geometries and acoustic conditions.
Innovation Solution
A method involving decorrelation and recorrelation transforms using phase-based transforms like the UHJ matrix to extract and manipulate ambient ambisonic coefficients, reducing correlation between background signals and optimizing compression and rendering for various audio formats.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If HOA background channels are directly encoded without decorrelation processing, then encoding simplicity is maintained, but compression efficiency deteriorates due to high correlation between background signals
Solution Approach 1:
The patent applies decorrelation processing as a preliminary step before encoding HOA background channels. By pre-processing the background signals to reduce correlation between channels, the encoding process becomes more efficient without requiring complex adaptive processing during compression. This preliminary decorrelation enables better compression ratios while maintaining manageable encoding complexity.
2Object-affected harmful factors
If HOA background signals are compressed with high correlation, then encoding complexity is reduced, but noise unmasking occurs leading to degraded audio quality
Solution Approach 1:
The patent implements decorrelation processing before compression to prevent noise unmasking. By reducing correlation between background channels in advance, the system avoids the harmful effect of noise unmasking that would otherwise occur during compression, thereby improving audio quality without requiring complex post-processing or adaptive noise management mechanisms.
3Productivity
If phase-based decorrelation transforms are applied to HOA background channels, then correlation between background signals is reduced improving compression, but processing time increases
Solution Approach 1:
The patent applies phase-based decorrelation transforms as a preliminary processing step that, while requiring computational resources, enables significantly better compression efficiency. The increased processing time is justified by the substantial improvement in compression ratios and the prevention of noise unmasking, making it suitable for offline or pre-processing scenarios where quality and efficiency are prioritized over real-time processing speed.
Data Source
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AI summary
In general, techniques are described for compression and decoding of audio data. An example device for compressing audio data includes one or more processors configured to apply a decorrelation transform to ambient ambisonic coefficients and obtain a decorrelated representation of the ambient ambisonic coefficients. The coefficients are extracted from a plurality of higher order ambisonic coefficients and represent a background component of the sound field described by the plurality of higher order ambisonic coefficients, wherein at least one of the plurality of higher order ambisonic coefficients is associated with a spherical basis function having an order greater than one.