The heart of VgCast  on-air solutions is a real-time multilayer composing engine. It supports virtually unlimited number of layered objects, and controls object contents, behavior and attributes. The types of objects are simple solid fills, gradient fills, text, still graphics, movies etc. Graphics and movies can contain alpha-channel used during composing. Layer position, size, transparency and other object-specific parameters can be changed dynamically.

Rendered frames are transferred to the presentation component of the engine. As a primary hardware VgCast supports family of Blackmagic Decklink boards, including multichannel adapters. There are a number of another presentation components, namely preview window, multihead VGA adapters, IP streaming, video file recorder etc.

VgCast engine acts as a server for any number of client applications. Clients communicate with the engine sending commands (unicode text strings) over TCP/IP. Such open architecture provides easy integration with a third-party applications. Of course, all standard VgCast components use this protocol to interact with the engine.