XACT (Cross-platform Audio Creation Tool) is an audio programming library and engine released by Microsoft as part of the DirectX SDK. It is a high-level audio library for authoring/playing audio that is written to use Xaudio on the Xbox, DirectSound on Windows XP, and the new audio stack on Windows Vista. Xaudio is an Xbox-only API designed for optimal digital signal processing. XACT also includes X3DAudio, a spatialization helper library available on both platforms, Windows and the Xbox. XACT was originally developed for Xbox development, and was later modified to work for Microsoft Windows development as well.

Support for XACT has been carried over from DirectX to XNA. The XACT Audio Authoring Tool is also available in XNA Game Studio Express.

The XACT Audio Authoring Tool is a companion application used to organize audio assets into wave banks (single files containing multiple WAV files) and sound banks (single files containing instructions for playing the WAV files in wave banks). The wave banks and sound banks for a project are subsequently called by XACT from within the application.

XACT Sound Creation Features

Support for the following formats: WAV, AIFF, XMA

Note: also supports embedded loop points in WAV and AIFF formats

16 and 8 bit PCM data

Supports Stereo and 5.1 speaker arrangements

Organisation of sounds

Multiple audio files can be grouped together into Wave Banks (XWB extension)

Cues and settings can be bundled with the Waves in Sound Banks (XSB extension)

Auditioning

Audio console window can be used to preview audio

Audio settings can be adjusted in-game (with debug mode libraries)

XACT API Programming Features

The API allows the integration of the wave, sound and cue information from the creation phase

In memory and streaming support

Audio event notification

Includes a code-driven API allowing lower level loading and playback of sounds without having to use all the XACT sound organisation features.

XACT Terminology and File Types

Sound Banks (.xsb) - a collection of sounds and cues.

Sounds - a sound has one or more waves together with properties like volume and pitch. Sounds are made up of tracks.

Tracks - tracks are made up events E.g. the simplest track has a Play Wave event

Events - various actions that take place within a track. Actions include: Play, Stop, Set Volume, Set Pitch etc.

Cues - a cue is used in code to trigger sounds. Each cue is made up of one or more sounds

Wave Banks (.xwb ) - a file format containing a collection of waves

Waves - the raw wave data in wav, aiff or xma format

Global Settings (.xgs) - defines rules and settings for sounds.

Categories - sounds can be assigned to a category (only one each) that specifies certain rules like number of instances along with settings like volume. You could create a category for the sounds of one character in your game so they all have the same volume. There are three predefined categories: global, default and Music.

Variables - these can be defined in the design stage and then referenced by the programmer in code to control Run-Time Parameter Controls

Run-Time Parameter Controls - also known as 'sliders'. These allow the control of sound parameters as the sound plays. For example they could be used to control the pitch of a car engine sound so as the accelerator is pressed the pitch is changed

DSP Effect Path Presets (DSPs) - allow effects like reverb to be applied to sounds

Compression Presets - compression can be applied to waves or wave banks

External references

XACT on MSDN