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Service Modules

Service modules are auxiliary components responsible for managing and providing the resources required by the Processing Models to execute binaural audio rendering algorithms efficiently.

About the service modules

We have made a major change to the service modules starting with version 3.0.0, in order to resolve limitations we had and also simplify the code. You can find the documentation for the previous service modules, present in the library up to version 2.5.0, at this link.

These resources include several key elements used during spatial audio processing:

  • Head-Related Transfer Functions (HRTFs), which simulate the direct sound path perceived by the listener model.
  • Binaural Room Impulse Responses (BRIRs), used to reproduce the reverberation characteristics of acoustic environments.
  • Source directivity data, which represent the directional radiation patterns of sound sources.
  • Second-order filter section (SOS) coefficients, which allow accurate modeling of, for example, near-field effects.
  • FIR filter coefficients, which can be used for headphone equalization or hearing-protection simulations.
  • Impulse responses of virtual loudspeakers in the Ambisonics domain, enabling simultaneous convolution and ambisonic decoding.
  • Geometric and acoustic descriptions of rooms, used to simulate acoustic environments.

Spatial organization

Most resources managed by the service modules are spatially indexed by azimuth, elevation, and distance.

Non-spatial resources are also supported, such as FIR coefficients for headphone compensation filters.

Together, these resources provide the foundation required to generate realistic and immersive binaural audio experiences.

Architecture Overview

The interaction between the main architectural components of the BRT framework is illustrated below.

flowchart TD

F[Models]
A[Processing Modules]
B[(Service Modules)]
C[Readers]
D[SOFA Files]
E[OBJ Files]

F -->|use different processing modules| A
A -->|request resources during rendering| B
B -->|get resources during rendering| A
C -->|pre-load data| B
D --> C
E --> C
  • Processing Models implement the binaural rendering algorithms.
  • Service Modules store and organize the spatial audio resources used by those algorithms.
  • Readers load the resources from external data formats.

Supported formats

The BRT library includes readers capable of loading spatial audio resources from SOFA and OBJ formats. For more details see the READERS section.

Available Service Modules

The following service modules are available for storing and managing spatial audio resources.

Module Description
SphericalFIRTable Stores FIR-based spatial data such as HRTFs, BRIRs, source directivity information, and general FIR filter coefficients.
SphericalInterpolatedFIRTable Stores HRTF and source directivity data and generates a regular spherical grid through interpolation, providing a predictable spatial structure.
SphericalSOSTable Stores second-order filter section (SOS) coefficients, which may be constant or vary depending on distance, azimuth, and/or elevation.
AmbisonicBRIR Stores the impulse responses of virtual loudspeakers in the ambisonic domain, enabling a pipeline where impulse response convolution and ambisonic decoding occur simultaneously.
Room Stores the geometric and acoustic description of a room, including its vertices, walls, and frequency-band absorption coefficients for each surface. An addition to the MTL format has been defined in order to store this acoustic information.