X3DAudio

X3DAudio is a software library that provides three-dimensional audio positioning for applications using Microsoft’s DirectX audio stack. It computes how sounds in a virtual 3D space should be rendered for a listener, producing a specialized channel matrix and DSP settings that feed into the output mix. The library supports features such as Doppler shift, distance-based attenuation, and directional sound cones, enabling more realistic spatial audio without implementing a full 3D audio engine from scratch.

The core concept of X3DAudio centers on a listener and one or more sound sources. The listener is defined by position, velocity, and orientation (typically front and top vectors), while each source includes position, velocity, and, optionally, directional cone parameters. Using these inputs, X3DAudio computes how much of each source’s signal should go to each output channel, how the perceived distance affects volume, and how Doppler effects should be applied. It also generates parameters for reverb routing if a reverb model is used. The calculations are designed to be hardware-agnostic, allowing developers to map the results to stereo, surround, or other speaker configurations.

Usage generally involves creating an X3DAUDIO_HANDLE, populating listener and source structures, and calling the X3DAudioCalculate function to obtain a channel matrix and DSP settings. The output is then applied to the audio pipeline, typically within XAudio2, to render the 3D sound in real time. X3DAudio is a component of the DirectX audio ecosystem and is commonly used in game development on Windows and Xbox platforms. It does not replace a full audio engine but provides a robust, portable basis for 3D audio positioning.