2.4.3 Sound Device and Driver Layers

Figure 2.11 illustrates a representative hardware configuration for a multimedia sound device.

Figure 2.11 Sound Device Hardware Configuration

As Figure 2.11 shows, the sound device is connected to a system DMA controller channel. The NT HAL coordinates access to the system's DMA controller or controllers and to appropriate DMA channels and/or registers for NT drivers of all slave DMA devices.

Figure 2.12 illustrates the corresponding driver for the sound device.

Figure 2.12 Sound Driver Layers

The system sound driver is both a highest-level and lowest-level NT driver that provides support for user-mode multimedia audio applications. The Multimedia component of the Win32 subsystem is layered between such an application and at least four system-supplied Win32 audio drivers: the wave-input, wave-output, midi-input, and midi-output drivers, which are implemented as dynamic-link libraries. Depending on its adapter, an NT sound driver also can provide support for a Win32 Aux driver that responds to applications' volume-control requests and/or for a Win32 mixer driver that supports multimedia mixer applications.