Not sure what your problem was with running out of memory on the 840av
It's exactly as you say: in 1993 terms you're talking about 15 grand in hardware before video capture was a reality on the mac. In modern terms, it's not 15 grand but it's still a bunch of specialized equipment that you have to find and then find documentation for or experiment with.
SGI could do it in a little less, but not
that much less.
It was much more reasonable on both sides by 1996-7 or so, and it was "imminently doable" for $2000 by 1999. Most of that has to do with better compression technologies combined with better hardware existing up front. (i.e. the stock disk on a blue-and-white G3 is much faster than the stock disk on a Quadra 840av or even a PowerMac 7500). Lots of PowerMac 8000 and 9000 configurations shipped with AV disk options as well, and they had the second/faster internal SCSI channel, and of course faster CPUs to do better compression up front.
RS232 or 422 control is a technique you can use to get away with it. The 840av has no problems grabbing, like, ten seconds worth of frames (worth noting: mine had 24, not 128 megs of RAM, at the time) at basically full quality, although in reality you would have worked with 320x240, which would make things a little easier too, so you'd start, capture the frames you could, and the computer would work on getting everything ready to get the next group of frames.
That would involve a pretty high end deck though, which would track for the 840 which itself was like a $5000 computer, give or take, but
wouldn't track for the LC/Performa 630 (which were sold pretty explicitly on the idea of home multimedia authoring) or even a 6200 or 7500. (Though, video in on the 6100/7100/7500/7600 was
mostly sold as a business-focused thing, for, like, video conferencing rather than as a multimedia authoring thing, in both of those cases the multimedia authoring computer was from the 8-series, not that it wasn't possible, just that Apple didn't market them that way or as noted by dcr configure them that way.)
Anyway - without support hardware like that on either side (or just moving to a much newer machine) you have to temper your expectations of what's reasonable or possible.
He has some high end gear and a couple DV decks for playback and he told me all DV recorders were junk from the day they came out and he has to make multiple passes sometimes to get a perfect grab without glitches. Could just be the tapes did not age well but he hates the format.
I used DV when it was under ten years old on pretty ho-hum hardware and this wasn't my experience, as far as I can remember.
The people I know who have DV stuff now talk about how poorly the tapes aged and so I suspect that's really it. DV will have
this kind of problem harder than, say, any VHS or beta/betacam or non-digital 8-based format will because of, well, its digital nature.
(Granted: it could be it had this problem in 2004 too and I never noticed because the glitches being described aren't noticeable at a glance, but I'm
guessing it's due to the format and the hardware aging being made worse by things being digital.)
Incidentally, DV
D seems to have aged better, as a format, despite being almost exclusively consumer-oriented. I got a mini-DVD-R/RW handycam from a thrift store some time last year and plugged it in and puttered around with it and the video imported with handbrake pretty much as well as it is possible for it to have done.
Another option for DV cameras is to record directly to hard disk-based recorders, via firewire, which was a thing that you could buy in the era, as a sort of prelude to video cameras with hard disks and flash memory card slots built in.
