Several of my friends worked on Intelligent Resources? Video Explorer NuBus card, which
could do realtime video capture and manipulation because it had some sort of video
processing and switching chip on the card. It also had an open bus that could be used to
connect multiple video-related cards together so they could bypass NuBus for sharing data.
(NuBus is only 10-40 MB/sec.)
I think AnimEigo was using a subtitling system built atop Video Explorer cards right up
until the switch to DVDs.
-- Chris