Hardware Reference
In-Depth Information
cards, 3D graphics cards, and so on. For gaming sound and graphics, Microsoft Windows
versions from Windows NT 4.0 and Windows 95 through Windows XP use a technology
called DirectX, which was introduced in December 1995. Starting with Windows Vista
(which uses DirectX 10), Microsoft Windows uses a new technology called Core Audio
APIs to control audio for all types of software. The following sections discuss DirectX
and Core Audio APIs.
DirectX and Audio Support Hardware
Microsoft's DirectX is a series of application programming interfaces (APIs) that sits
between multimedia applications and hardware. Unlike MS-DOS applications, which re-
quired developers to develop direct hardware support for numerous models and brands
of audio cards, video cards, and game controllers, Windows applications use DirectX to
“talk” to hardware in a more direct manner than normal Windows drivers do. This im-
provesprogramperformanceandfreesthesoftwaredeveloperfromtheneedtochangethe
program to work with different devices. Instead, a game developer must work with only
the DirectX 3D renderer, and other DirectX interface routines. Until the introduction of
DirectX 10 with Windows Vista, audio programming was also part of DirectX.
For more information about DirectX,
see
“
Microsoft DirectX 9
,
”
p.
636
(
Chapter 12
,
“
Video Hardware
”
).
Core Audio APIs for Windows Vista and Windows 7
Although Windows Vista's changes to the desktop are well-known, an equally significant
change in Windows Vista is how it works with audio. DirectX 10, the native version of
DirectX included in Windows Vista, no longer includes audio application programming
interfaces (APIs) such as DirectSound and DirectMusic. These and other audio-oriented
APIs now interface with Windows via the new Core Audio APIs originally introduced
in Windows Vista (see
http://msdn.microsoft.com/en-us/library/dd370784(v=vs.85).aspx
)
and improved in Windows 7. These APIs include:
• Multimedia Devices (MMDevice) API—Clients use MMDevice to enumerate the au-
dio endpoint devices in the system.
•WindowsAudioSessionAPI(WASAPI)—Clients useWASAPItocreate andmanage
audio streams coming to or from audio endpoint devices.
• DeviceTopology API—Clients use DeviceTopology API for direct access to features
such as volume controls and multiplexers along the data paths of hardware devices in-
side audio adapters.
