Re:The 1990s Amiga with Video Toaster has a VFX cool factor ...
by pjc50 on Tuesday July 25, 2023 @05:11AM
(#36859825)
> Did it simply come down to the coincide of the system clock being a multiple of the NTSC signal?
Not a coincidence, and there was also an additional hardware feature: the "genlock".
Normally when doing graphics generation your software keeps track of the "vertical blanking interrupt", which tells you when a new frame has started. Normally this is generated internally. The Amiga let you lock the output video generation to an input video signal, so you could draw over a TV signal without having to digitize the incoming signal or use some sort of external chromakey system.
Not a coincidence, and there was also an additional hardware feature: the "genlock".
Normally when doing graphics generation your software keeps track of the "vertical blanking interrupt", which tells you when a new frame has started. Normally this is generated internally. The Amiga let you lock the output video generation to an input video signal, so you could draw over a TV signal without having to digitize the incoming signal or use some sort of external chromakey system.