Parametric Ambience Replication for Low Bit Rate HOA Compression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current low bit rate compression methods for Higher Order Ambisonics (HOA) sound field representations result in spatially sparse reconstructions, leading to a dry and quieter sound, especially when using a small number of quantized signals, which fails to properly reconstruct ambient sound fields.
Innovation Solution
The Parametric Ambience Replication (PAR) method creates new uncorrelated signals with modified phase spectra to replicate missing ambient components, enhancing the HOA representation by superimposing them with the original sparse representation, matching spatial acoustic properties, and reducing side information through complex-valued mixing matrices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If low bit rate compression is applied to HOA representation, then data rate is reduced, but spatial resolution and sound quality deteriorate due to spatially sparse reconstruction
Solution Approach 1:
The patent creates artificial copies of ambient sound field components by generating pseudo-random HOA coefficient sequences that replicate the statistical properties of original ambient signals. These synthesized copies are then combined with directional components to reconstruct a complete HOA representation that maintains spatial resolution while using low bit rate compression for transmission.
2Productivity
If a small number of quantized signals are used for compression, then compression efficiency is improved, but ambient sound field reconstruction fails leading to dry and quieter sound
Solution Approach 1:
The patent introduces an intermediary processing stage that separates the HOA representation into directional components (preserved from quantized signals) and ambient components (synthesized from statistical parameters). This intermediary decomposition allows efficient compression of directional information while generating reliable ambient sound fields through statistical reconstruction, preventing the dry and quieter sound effect.
3Loss of energy
If HOA representation is compressed to low bit rate, then transmission bandwidth is reduced, but the number of expansion coefficients required for spatial resolution increases
Solution Approach 1:
The patent segments the HOA coefficient set into two distinct groups: directional coefficients (which are sparsely represented and quantized) and ambient coefficients (which are synthesized from statistical parameters like covariance matrices). This segmentation allows transmission of only essential directional information at low bit rate, while ambient components are regenerated at the receiver using compact statistical descriptors, thereby reducing transmission bandwidth while maintaining spatial resolution.
Data Source
Figure 1~4
Figure 2
Figure 3
AI summary
The invention is suited for improving a low bit rate compressed and decompressed Higher Order Ambisonics HOA signal representation of a sound field, wherein the decompression provides a spatially sparse decoded HOA representation and a set of indices of coefficient sequences of this representation. From reconstructed signals of the original HOA representation a number of modified phase spectra signals are created using de-correlation filters, which modified phase spectra signals are uncorrelated with the signals of said original representation. The modified phase spectra signals are mixed with each other using predetermined mixing parameters, in order to provide a replicated ambient HOA component. Finally the spatially sparse decoded HOA representation is enhanced with the replicated time domain HOA representation.