Binaural Ambisonics Decoder Tapering Window
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Solution Overview
Problem
Converting spherical harmonics (SH) representations to binaural sound signals introduces inaccuracies due to truncation of higher order SH coefficients and head-related transfer function (HRTF) filters, leading to spectral coloration, left-right confusion, and front-back confusion in spatial sound reproduction.
Innovation Solution
A computer-executable decoder uses a tapering window function and a coloration compensation filter to generate binaural sound signals from SH representations, reducing inaccuracies by applying the tapering window function directly to the HRTF filters or incorporating it into the decoder, thereby minimizing the impact of SH encoding order truncation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If higher SH encoding orders are used to improve spatial bandwidth and accuracy, then spatial sound reproduction quality is improved, but computational resources and data rates required for decoding increase
Solution Approach 1:
The patent extracts and removes higher order SH coefficients from the SH representation that contribute most to spectral coloration and localization errors. By selectively truncating these coefficients and applying compensation filters, the system achieves accurate spatial reproduction with reduced computational requirements compared to using full high-order SH representations.
Solution Approach 2:
The patent changes the parameter of SH encoding order by using adaptive truncation based on spatial frequency content. Instead of uniformly using high encoding orders for all frequency ranges, the system dynamically adjusts the effective encoding order - using lower orders where sufficient and higher orders only where necessary - thereby reducing overall computational burden while maintaining accuracy where needed.
2Measurement precision
If higher SH encoding orders are used to improve spatial bandwidth, then spatial diversity and acuity are improved, but data rates required for decoding increase
Solution Approach 1:
The patent extracts only the essential higher order coefficients that provide spatial bandwidth benefits while removing redundant coefficients that contribute to spectral coloration. This selective extraction reduces the data rate required for transmission and storage while preserving the spatial diversity and acuity needed for accurate sound reproduction.
3Use of energy by moving object
If conventional decoding methods are used, then computational resources are reduced, but spectral coloration and localization errors increase
Solution Approach 1:
The patent applies preliminary action by pre-computing and storing compensation filters that account for spectral coloration and localization errors. These filters are designed offline based on the known characteristics of HRTF filters and SH basis functions. During runtime, the system only needs to apply these pre-computed filters, which requires minimal computational resources while effectively correcting the errors that would otherwise require complex high-order decoding.
Solution Approach 2:
The patent introduces compensation filters as an intermediary element between the truncated SH representation and the final binaural output. These filters act as a mediator that corrects the spectral coloration and localization errors introduced by truncation, enabling accurate spatial reproduction with lower computational requirements than conventional high-order decoding methods.
4Measurement precision
If HRTF filters with high spatial bandwidth are used, then binaural reproduction accuracy is improved, but the impact of truncation errors increases
Solution Approach 1:
The patent converts the harmful effect of truncation errors into a benefit by designing compensation filters that specifically target and correct the spectral coloration and localization errors caused by truncation. Rather than trying to avoid truncation entirely (which would require excessive computational resources), the system embraces truncation as a necessary simplification and then compensates for its effects, turning what was a harmful limitation into an acceptable trade-off that enables efficient accurate decoding.
Data Source
AI summary
A computing system that facilitates decoding a spherical harmonics (SH) representation of a three-dimensional sound signal to a binaural sound signal is described herein. The computing system generates a binaural sound signal based upon the SH representation, a tapering window function that is selected based on an SH encoding order of the SH representation, and a coloration compensation filter that incorporates the tapering window function. The computing system causes the binaural sound signal to be played over at least two speakers.