Introduction to USB Video Class Extension Units
The USB Video Class specification defines a mechanism to extend the functionality of devices that comply with that specification and describes the behavior of Extension Units. Independent hardware vendors (IHVs) can enhance the value of their devices by adding functionality that goes beyond that described in the specification.
This extension mechanism requires operating system support and some user-mode plug-ins so that applications can work with these extensions. The USB Video Class driver architecture provides such a mechanism so that IHVs can expose extended device functionality as COM APIs. This documentation describes the steps required to create and register such a plug-in.
IKsTopologyInfo, ISelector and IKsNodeControl are defined in Vidcap.h.
In Windows Vista and later releases, Vidcap.h is included as part of the Microsoft Windows SDK.
The Microsoft DirectShow documentation contains the corresponding reference pages. Globally unique identifier (GUID) types and some other USB-video-related constants are defined in Ksmedia.h. For more information, see USB Video Class Properties and Kernel Streaming Topology Nodes.