HOA Compression With Dynamic Channel Allocation for Lower Bit Rates
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Solution Overview
Problem
Existing Higher Order Ambisonics (HOA) compression methods are inefficient in optimizing the use of channels for perceptual coding, leading to suboptimal directional-ambient decompositions and high bit rates, particularly in streaming applications.
Innovation Solution
A method and apparatus that dynamically assign directional signals and ambient HOA coefficient sequences to a fixed number of channels based on perceptual relevance, using a criterion that minimizes perceptible error by considering the spatial power distribution of quantization noise and modeling errors, allowing channels to be flexibly allocated between directional and ambient components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If HOA representation uses higher expansion order N to improve spatial resolution, then sound field representation quality is improved, but the number of expansion coefficients grows quadratically leading to high bit rates
Solution Approach 1:
The patent segments the HOA coefficient sequences into two distinct groups: directional components (representing dominant sound sources) and ambient components (representing the surrounding sound field). This segmentation allows different compression strategies to be applied to each group, reducing the overall bit rate while maintaining spatial resolution quality.
Solution Approach 2:
The patent extracts and identifies dominant directional signals from the HOA representation, separating them from the ambient components. By taking out the most perceptually relevant directional information, the remaining ambient components can be represented with fewer coefficients, thereby reducing the total number of coefficients that need to be transmitted.
2Ease of manufacture
If traditional HOA compression codes each coefficient sequence individually, then compression is straightforward, but bit rates remain high and compression efficiency is suboptimal
Solution Approach 1:
The patent merges the compression of directional and ambient components into a unified perceptual coding framework. By combining these previously separately handled components into a single compression process that considers their interaction, the patent achieves better overall compression efficiency and lower bit rates while maintaining perceptual quality.
Solution Approach 2:
The patent introduces dynamic adaptation in the compression process by adjusting the number of coefficients allocated to directional versus ambient components based on the actual sound scene characteristics. This dynamic allocation optimizes compression efficiency for different types of audio content, achieving lower bit rates compared to static compression methods.
3Ease of operation
If fixed number of channels is used for perceptual coding, then channel allocation is simple, but it cannot adapt to varying directional and ambient signal content
Solution Approach 1:
The patent implements dynamic channel allocation where the number of channels assigned to directional versus ambient components is adjusted based on the analyzed sound scene characteristics. This dynamic approach allows the system to adapt to varying signal content while maintaining a fixed total number of channels, optimizing perceptual quality for different audio scenarios.
Solution Approach 2:
The patent employs feedback mechanisms where the compression process analyzes the directional and ambient signal content and uses this information to determine optimal channel allocation. The analysis results feed back into the compression stage, enabling adaptive channel assignment that responds to the actual signal characteristics rather than using a fixed predetermined allocation.
Data Source
AI summary
Higher Order Ambisonics represents three-dimensional sound independent of a specific loudspeaker set-up. However, transmission of an HOA representation results in a very high bit rate. Therefore, compression with a fixed number of channels is used, in which directional and ambient signal components are processed differently. The ambient HOA component is represented by a minimum number of HOA coefficient sequences. The remaining channels contain either directional signals or additional coefficient sequences of the ambient HOA component, depending on what will result in optimum perceptual quality. This processing can change on a frame-by-frame basis.