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Wavelet-Based Spatial Audio Format

Ambisonics is a spatial audio technique covering all steps of the audio production chain, from encoding and recording to transmission and decoding, whose building blocks are the spherical harmonics. Some of the drawbacks of low order Ambisonics, like large source spread and small sweet-spot, are directly related to the fact that spherical harmonics do not have compact support on the sphere. In this paper we propose a novel spatial audio format similar in spirit to Ambisonics but which replaces the spherical harmonics by an alternative set of functions with compact support, the spherical wavelets.We develop a complete audio chain from encoding to decoding, using discrete spherical wavelets built on a multiresolution mesh, illustrating with an example implementation of the format. We present a decoding algorithm optimizing acoustic and psychoacoustic parameters that can generate decoding matrices to irregular layouts for both Ambisonics and the new wavelet format. This audio workflow is directly compared with Ambisonics. For an industry-standard loudspeaker layout, we show how we can reach well localized sound sources with almost no negative gains (which are a common issue in most Ambisonics decoder designs). The approach is very flexible: there are different possible incarnations of the wavelet-based audio format, depending on the specific multiresolution mesh and the wavelet family, making possible to customize the format, for example adapting it tomeshes that closely resemble the distribution of loudspeakers in standard layouts.

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JAES Volume 68 Issue 9 pp. 613-627; September 2020
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Permalink: http://www.aes.org/e-lib/browse.cfm?elib=20893

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AES - Audio Engineering Society