Game Development Reference
In-Depth Information
Microsoft XACT and XAudio2
Microsoft Direct Music
Producer
XACT in action.
Microsoft has taken great strides to provide audio tools to specii cally
leverage the features of its audio libraries, beginning with Direct
Music Producer (see sidebar), and extending to the Xbox and Xbox
360 consoles in the form of XACT. Some of the standout additions to
the engine and tool include the ability to author sound propagation
curves, global variables including Doppler and speed of sound, real-time
parameter control, and Reverb presets. Unfortunately Microsoft has since
chosen to discontinue XACT (along with the free XNA game engine that
it also supported) for both Windows 8 and the new Xbox One, leaving
Microsoft-oriented developers and implementers with no graphically-
based tools from the company to use.
Direct Music Producer, though
primitive, was one of the i rst
middleware applications regularly used
in Windows games.
Based on the Microsoft Direct Music/
Direct Sound for PCs, the Direct
Music Producer enabled interactive
functionality using the features of the
low-level audio libraries in Direct X.
This included the ability to loop i les,
specify random or sequential playback
behavior, create sample banks (DLS),
and specify parameters for interactive
playback using MIDI.
However, the API that supports this new architecture, called XAudio2,
is still going quite strong. Introduced in 2008 to replace DirectSound
and XAudio, XAudio2 is a much more advanced audio library of ering
high-level performance. Signii cantly, it takes a somewhat more
unique approach to sound generation by separating the sound
data from its application in the mixing and processing setup. This
means that multiple sounds can be potentially be mixed into a single
stream, thus saving on CPU and memory. Another library called
WASAPI (Windows Audio Session API) is benei cial for extremely
low-latency 32-bit l oating point audio, and is used primarily for
middleware-oriented developers, rather than sound designers or
game programmers.
