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A Matlab implementation of the Higher-order Spatial Impulse Response Rendering (HO-SIRR) algorithm. An alternative approach for reproducing Ambisonic IRs over loudspeakers.
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README.md

HO-SIRR

Higher-order Spatial Impulse Response Rendering (HO-SIRR).

(Please note that the code is currently very much "work in progress". Feedback is most welcome!)

Getting Started

The code is reliant on the following Matlab libraries:

The HO-SIRR script should be configured, for example, as:

pars.order = 3; % transform order of input signals  
pars.fs = 48e3; 
pars.ls_dirs_deg = ???; % your loudspeaker dirs, [azi elev], in degrees

% Specify windowing sizes for multi-resolution STFT, for example:
pars.multires_winsize = [1024 128 16]; 
pars.multires_xovers = [500 2e3]; % 1024 up to 500Hz, then 128 up to 2kHz, then 16 past 2kHz (Note HOSIRR uses 50% window overlap)

% Diffuse rendering parameters
pars.RENDER_DIFFUSE = 1;     % 0: disable diffuse rendering, 1: enable
pars.decorrelationType = 'noise'; % {'phase','noise'}, decorrelation via convolution with 'noise', or via randomising the 'phase'
pars.maxDiffuseAnalysis_Hz = 6e3; % frequency up to which to estimate the diffuseness parameter 
pars.alpha_diff = 0.975;     % minimum diffuseness averaging coefficient (one-pole filter)

% Optionally, the first highest N peaks of the response may be isolated
% and pnned with a broad-band 
pars.BROADBAND_DIRECT = 1;   % 0: disabled, 1: enabled
pars.nBroadbandPeaks = 1;    % number of peaks to isolate 

The input Ambisonic signals (ACN/N3D) may be rendered for the loudspeaker set-up as:

shir = audioread( ??? ) % load input audio, which should use ACN/N3D conventions
[lsir, lsir_ndiff, lsir_diff, pars, analysis] = HOSIRR(shir, pars);
% lsir       - output loudspeaker impulse responses
% lsir_ndiff - output loudspeaker impulse responses, direct stream only
% lsir_diff  - output loudspeaker impulse responses, diffuse stream only
% pars       - output parameters
% analysis   - analysed parameters stored during rendering

3 Developers

  • Leo McCormack - Matlab programmer and algorithm design (contact: leo.mccormack@aalto.fi)
  • Archontis Politis - Matlab programmer and algorithm design
  • Ville Pulkki - algorithm design

4 License

This code is provided under the BSD 3-clause license.

References

[1] McCormack, L., Politis, A., Scheuregger, O., and Pulkki, V. (2019). "Higher-order processing of spatial impulse responses". In Proceedings of the 23rd International Congress on Acoustics, 9--13 September 2019 in Aachen, Germany.

[2] Politis, A. and Pulkki, V., 2016. "Acoustic intensity, energy-density and diffuseness estimation in a directionally-constrained region". arXiv preprint arXiv:1609.03409.

[3] Merimaa, J. and Pulkki, V., 2005. "Spatial impulse response rendering I: Analysis and synthesis". Journal of the Audio Engineering Society, 53(12), pp.1115-1127.

[4] Pulkki, V. and Merimaa, J., 2006. "Spatial impulse response rendering II: Reproduction of diffuse sound and listening tests". Journal of the Audio Engineering Society, 54(1/2), pp.3-20.

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