DirectMusic DDI Overview

The design principles that are needed to implement user-mode synths generally apply to kernel-mode synths as well. For this reason, this guide begins with a discussion of user-mode implementations and progresses to specific kernel-mode topics.

Typically, the best design strategy is to first write a software implementation of the DirectMusic device driver interface (DDI) that runs in user mode. This approach is beneficial even if the final product is a kernel-mode implementation that uses hardware components. After the user-mode version is completed, the software can be converted to kernel mode and connections established with the hardware, one feature at a time. For more information, see User Mode Versus Kernel Mode.

DirectMusic uses the following user-mode interfaces to control user-mode synthesizers and communicate with kernel-streaming drivers:

IDirectMusicSynth

This is the user-mode interface for implementing custom software synths.

IDirectMusicSynthSink

This is the user-mode interface for implementing custom wave sinks in Microsoft DirectX 6.1 and DirectX 7. In DirectX 8 and later, DirectMusic always uses its private wave sink with a user-mode synth, and no public interface is supported for user-mode wave sinks.

IKsControl

DirectMusic uses this interface to access the properties of kernel-streaming drivers from user mode in DirectX 6.1 and later.

Kernel-mode terminology differs slightly from user-mode because of the port-miniport driver model (see Introduction to Port Class), which delegates generic kernel-streaming tasks to the DMus port driver and assigns hardware-specific functions to the DMus miniport driver. The port and miniport drivers share responsibilities for the synth. The kernel-mode wave sink is part of the kernel-resident port driver. Unlike the user-mode wave sink in DirectX 6.1 and DirectX 7, the kernel-mode wave sink is not replaceable. Most of the work that is required to build a custom kernel-mode driver is in the writing of the miniport driver. In most cases, the miniport driver is the only component that the driver writer needs to implement to support a piece of hardware, or to implement a custom software synth for DirectMusic.

Custom DMus miniport drivers use the following kernel-mode interfaces:

IAllocatorMXF

IMiniportDMus

ISynthSinkDMus

IMXF

IMasterClock

IPortDMus

DMus miniport drivers implement the IMiniportDMus, ISynthSinkDMus, and IMXF interfaces. The DMus port driver implements the IAllocatorMXF, IMasterClock, and IPortDMus interfaces and exposes them to miniport drivers.

 

 

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