Video for Windows (VfW) The first video capture and display system developed by Microsoft for the Windows operating system. The design of VfW video capture was optimized for capturing movies to disk. Features important to video conferencing, TV viewing, capture of video fields, and ancillary data streams are missing from the VfW architecture. To circumvent these limitations, vendors augmented VfW by implementing proprietary extensions. However, without standardized interfaces, applications that use these features must include hardware-dependent code.

With the integration of DVD, MPEG decoders, video decoders and tuners, video port extensions (VPE), and audio codecs on single adapters, a unified driver model that supports all these devices and handles resource contention simplifies development efforts.

The stream class driver provides a framework for addressing these issues. It supports a uniform streaming model for standard and custom data types. Similarly, property sets for most standard devices are defined and can easily be extended if needed. Because the stream class follows WDM streaming conventions, it supports data transfer between kernel drivers without requiring a thread to transition to user mode. Thus there is no decrease in system performance associated with thread context switches between user-mode and kernel-mode.

Due to the large installed base of VfW applications, it is anticipated that VfW drivers will continue to flourish for devices that are primarily used for capturing movies. Capture devices that are used primarily for TV viewing and video conferencing are expected to migrate more quickly from the VfW model to the WDM streaming model.

To bridge the VfW and WDM worlds, a mapper is provided as part of the operating system. This component, called the VfW-to-WDM mapper, makes WDM drivers appear as VfW drivers for legacy applications.

Virtualdub uses only VfW drivers, not the newer WDM interface. MS Info