A system and method for substituting data packets into a data stream, is provided. In one embodiment, the data stream is a video data stream. The system includes packet buffers, a multiplexer, a packet substitution controller, a direct memory access (DMA) engine and a link list buffer controller. A method is also provided for substituting data packets--containing information of the same or different type--into a video data stream at variable rates using a selection mechanism driven by link list buffer control.