Sub-band Matrix Filtering for Binaural Playback
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Solution Overview
Problem
Current methods for processing sound data in multichannel formats, such as 5.1, to achieve a 3D spatialization effect called 'Virtual Surround' are complex and do not accurately replicate the spatial perception of sound events, particularly when using binaural or Transaural playback, as they require multiple filters and do not retain the original timbre of the sound.
Innovation Solution
A method for dual-channel playback that applies matrix filtering using specific transfer functions for ipsilateral and contralateral paths, with a multiplicative coefficient defined by the spectrum of the contralateral transfer function deconvolved with the ipsilateral transfer function, reducing complexity and preserving the timbre of the sound by eliminating coloration distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple filters are used to achieve 3D spatialization effect in binaural playback, then spatialization quality is improved, but processing complexity increases
Solution Approach 1:
The patent extracts and eliminates the ipsilateral transfer function filters from the processing chain, retaining only the contralateral HRTF filters. This reduction from multiple filters to fewer filters maintains spatialization quality while significantly lowering processing complexity and computational burden.
Solution Approach 2:
Instead of applying both ipsilateral and contralateral filters as in conventional approaches, the patent inverts the approach by applying only contralateral filters and using the deconvolved spectrum as a multiplicative coefficient. This inverted approach achieves the same spatialization effect with reduced complexity.
2Measurement precision
If conventional binaural processing is applied, then spatialization effect is achieved, but original timbre of sound is lost due to coloration distortion
Solution Approach 1:
The patent converts the harmful coloration distortion introduced by conventional HRTF filtering into a beneficial approach by using the deconvolved spectrum as a multiplicative coefficient. This transforms the filtering process into a method that preserves timbre while maintaining spatialization effects.
Solution Approach 2:
The patent changes the parameter approach by using the deconvolved spectrum of the contralateral transfer function as a multiplicative coefficient rather than direct filtering. This parameter change allows the system to maintain the spectral characteristics of the original sound (timbre) while achieving the desired spatialization effect.
3Measurement precision
If conventional HRTF filtering is applied to all channels, then spatial perception is improved, but processing time increases
Solution Approach 1:
The patent extracts and removes the computationally intensive ipsilateral filter applications, retaining only the contralateral HRTF filter applications. This extraction significantly reduces processing time while maintaining spatial perception quality through the use of deconvolved spectral coefficients.
Data Source
AI summary
Processing of sound data encoded in a sub-band domain, for dual-channel playback of binaural or Transaural® type is provided, in which a matrix filtering is applied so as to pass from a sound representation with N channels with N>0, to a dual-channel representation. This sound representation with N channels comprises considering N virtual loudspeakers surrounding the head of a listener, and, for each virtual loudspeaker of at least some of the loudspeakers: a first transfer function specific to an ipsilateral path from the loudspeaker to a first ear of the listener, facing the loudspeaker, and a second transfer function specific to a contralateral path from said loudspeaker to the second ear of the listener, masked from the loudspeaker by the listener's head. The matrix filtering comprises a multiplicative coefficient defined by the spectrum, in the sub-band domain, of the second transfer function deconvolved with the first transfer function.