Plugin SDK

VirtualDub has the capability to load third-party DLLs that include their own video filters. The filters that are built into VirtualDub use the same interface that is exported to DLLs, so you can write filters similar to or better than the included ones. You can sample some of these at the third-party filters page; these range from corrective filters, such as noise reducers, to synthesis filters, such as the subtitler. The basic interface is simple to work with: VirtualDub gives you a 32-bit ARGB bitmap to modify. You can also create modules that include input drivers, which enable VirtualDub to read new video and audio file formats.

Requirements for the Plugin SDK:

Microsoft Visual C/C++ 6.0 or newer, any edition. Visual C++ 6.0 Service Pack 5 Professional or Visual Studio 2005 are recommended; Express editions, including Visual C++ Express 2005 and 2008 may be used. Other C++ compilers may be usable but are not supported.
VirtualDub 1.4.12 or newer (VirtualDub 1.8.8+ recommended).

Download Plugin SDK 1.1 (VDPluginSDK-1.1.zip) Download Plugin SDK 1.0 (VDPluginSDK-1.0.zip)

The Plugin SDK supercedes the old Filter SDK, which only covered older versions of the 32-bit video filter API, and doesn't cover 64-bit video filters or input plugins. If you have an old filter which you need to recompile, you may need to use this older filter SDK:
Download filter SDK 1.05 (filtsdk-1.05.zip, 66K zip file)