https://youtu.be/OXT5MrDdyB8?si=cZChImbAi3JBbFFl&t=49
This also gives me a bit more understanding of how the Video Toaster was possible to architect in a day with such slow CPU clock speeds. It seemed like magic at the time compared to limited capabilities of IBM PC clones. I hadn't realized how much capabilities these other Amiga chips provided.
If another non-genlockable computer could have generated the remapping addresses fast enough in those days, a Toaster-like device could have been designed to work with it. It just would have had to include a full separate genlock and the output would have been delayed a frame to allow that circuit time to work. So, it was possible, it just would have cost a bit more. How much more? Around that time, separate genlock cards capable of syncing up two disparate video sources sold for around $1,000.
On the other hand, an interactive, real-time address generator capable of keeping up with full video speeds would have cost tens of thousands of dollars. For example, the Quantel Mirage cost $700,000 in the 1980s and didn't even generate its addresses in real-time. The Mirage pre-rendered all the remapping addresses to a massive RAM disk using a Pascal program running on a workstation (which could take an hour or more) and only played them back on cue. The real-time part of the Mirage's hardware just digitized live video input and mapped it to the fixed stream of pre-generated addresses. Thus the Mirage could apply complex effects to live video but the effect geometry had to be canned, not interactive. The Ampex Digital Optics hardware did generate addresses in real-time entirely in logic-gate based hardware. Take a look at the ADO patent to gain an appreciation for just how insanely hard it was for 1980s era pre-GPU hardware to generate addresses at broadcast video rates. (https://patents.google.com/patent/US4472732/en) In fact, these esoteric real-time broadcast video effects systems were some of the first steps toward GPUs. According to Ken Kutaragi, Sony's $350,000 System-G 3D video effects hardware (which reportedly had worldwide sales of... three units) led to the Playstation GPU.
The Toaster effects could be interactive because it relied on the Amiga's graphics output as its address generator. In fact, the Amiga computer's monitor output was normally used to display the Toaster user interface but when a video effect was running the interface was entirely replaced with odd patterns that looked like bar codes. These were the addresses being generated by the Amiga custom chips and fed from the Amiga to the Toaster hardware in real-time via the monitor output (technically the fastest 'bus' in the system). This was a remarkable hack which required the Toaster to be very tightly coupled with the Amiga's hardware design and also involved some other extremely clever trade-offs. Relying on the Amiga's graphics output as the real-time address generator enabled the Toaster to exist and was also why the Toaster could never be ported to another computer or even to the PAL video standard. The Amiga's genlockability just allowed the Toaster to be even less expensive.
No way, that’s why the wipes took over the switcher screen and where that peculiar vertical line pattern came from?
I can still remember these with an odd intensity from playing with the Toaster at the studio where my dad worked 30 years ago.
I'll never forget seeing a group of Japanese engineers from Sony who designed high-end video effects hardware (which cost >20x what a Toaster system did) seeing the Toaster at the NAB trade show for the first time. There was nothing but stunned silence and shocked looks... then after a long while of watching the demo and seeing the interface turn into weird garbage during each effect, you could see the light dawn on their faces - and then the whole group erupted into excited, highly-animated chatter. I've never wished I spoke Japanese as much as that moment :-).
Trivia: He's the brother of Dana Carvey, and Garth wears a Video Toaster T-Shirt in Wayne's World 2.
Even the CGA card of an IBM PC could have been modified in this way. I can imagine a hack where the flash attribute in text mode gets used to act as the overlay key, but it would have been pretty darned ugly.
Of course the very thing made genlock work so well on the Amiga (the use of bitplanes) was a factor in the ultimate demise of the Amiga in the 1990s. It's funny how the memory bandwidth tradeoff changes things.