Seems like I've given these forums short shrift, but have a look at what I've been investigating over the past couple weeks while gradually chipping away at the stuff necessary to put together a belated 25th-Anniversary video:
For those who aren't familiar with the overall backstory, a bunch of really crazy, and really brilliant, people decided to go and come up with a way of preserving Laserdiscs in exactly the way that I envisioned happening like 15 years ago: Tap the laser pickup, capture a raw stream of the data, and then post-process it in software.
As a result, via the "Domesday Duplicator" hardware platform, there's now the ld-decode project: https://github.com/happycube/ld-decode
The initial point that I was blocked on was worrying about the fact that the chroma decoder would only handle active video lines, and the existing LD captures in MAME require raising the upper "bar" of decoded lines to include VBI data. Except about a week ago, after 5 minutes of investigation, it turned out that doing so is as easy as adjusting a few variables that define the active starting lines for both fields and frames.
Currently, the main blockers are that there are some audio decoding issues. Time Traveler in particular is hit pretty hard, as there's mysterious distortion that can't be ascribed to waveform clipping, and also doesn't seem to involve CX companding. So for now, things are at a standstill until the resident audio genius on the ld-decode project can nail down what's going on. After that, though, it's pretty turnkey to bring these captures into MAME.
ld-decode is a project that stands to have as much of an impact for A/V as the people working on magnetic-flux captures have had for disk media, yet it's always seemed to have a very small but hard core of developers. I'm hoping that by promoting it a bit more, there might be a few more folks who come on board to lend their skills.
But suffice it to say that what already exists is killer: There's even support for "disc stacking": It's known that at this point, it's pretty common for Laserdiscs to suffer from disc rot. But if you can stack multiple captures from multiple discs of the same production run, the toolchain supports a best-case voting process in order to completely eliminate dropouts that only occur in a minority of discs, since the dropout locations are fairly random.
This doesn't just benefit MAME, it benefits the Daphne and Singe projects as well. This rising tide raises all boats, and I couldn't be more excited about it.