/System/Library/Frameworks/CoreMediaIO.framework/Versions/A/Resources/IIDC.plugin/Contents/Resources/IIDCVideoAssistant IIDCVideoAssistant is used by the CoreMediaIO Device Abstraction Layer Plug-In that provides video capture from external Apple FireWire (IEEE 1394) iSight cameras and third-party FireWire IIDC-class cameras using AVFoundation Capture APIs. The process allows multiple applications to simultaneously capture from the same camera.
The binary is a part of CoreMediaIO public framework.