Ambisonic to Binaural Audio Conversion via HRIR Symmetry Mapping
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Solution Overview
Problem
Existing methods for converting ambisonic audio to binaural audio for personal audio delivery devices, such as headphones, fail to accurately spatialize sound due to the assumption of symmetry in head-related impulse responses (HRIRs), which does not account for the asymmetric nature of human ears, leading to inaccurate representation of sound directions.
Innovation Solution
The method involves using HRIRs associated with sound sources located symmetrically with respect to the head of the listener, equivalently mapping these HRIRs to HRIR pairs associated with sound sources on one side of the head, and converting them into spherical harmonics to improve spatialization of binaural audio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If symmetry assumption is used in HRIR processing, then device complexity is reduced, but measurement precision of sound direction deteriorates
Solution Approach 1:
The patent applies asymmetry by using different HRIRs for left and right ears instead of assuming symmetry. Specifically, it uses HRIRs measured or synthesized for each ear independently, and applies different spherical harmonic coefficients to each ear's audio signal, thereby accurately representing the asymmetric nature of human ears and improving sound direction precision.
2Productivity
If HRIRs for symmetric sound sources are mapped to one-sided HRIR pairs, then processing efficiency is improved, but spatialization accuracy deteriorates
Solution Approach 1:
The patent applies local quality by allowing different spherical harmonic coefficients for left and right ears. Instead of using a single set of coefficients for both ears, it calculates and applies ear-specific coefficients that reflect the local asymmetry of each ear's acoustic response, thereby improving spatialization accuracy while maintaining processing efficiency through selective differentiation.
Data Source
AI summary
Ambisonic audio is converted to binaural audio based on head related impulse responses (HRIRs) associated with sound sources located symmetric with respect to a head of a listener. The HRIRs associated with sound sources located symmetric with respect to the head of the listener are mapped to HRIR pairs associated with sound sources located on one side of the head of the listener based on the symmetry of the sound source locations. A sequence of HRIRs based on the mapped left HRIRs or a sequence of HRIRs based on the mapped right HRIRs are input into a spherical harmonics converter which outputs respective left spherical harmonics or right spherical harmonics. Ambisonic audio is binauralized based on the left spherical harmonics and the right spherical harmonics.