Thanks for the visits and posting some explanations as well.
-- The duplicator's ADC is 10-bit unsigned; the FPGA converts this to scaled 16-bit signed data (as 16-bit is the only thing the USB3 can pass - you have to transfer 16-bit anyway). Since there is no processing of the sample by the Linux app, that is what is stored on the hard drive.
So you have NTSC capture at 28.63 MSPS @ 16-bit and PAL capture at 35.47 MSPS. The size of the sample depends on the length of the disc, so it's approximately:
1 second NTSC = (2 bytes * 28,630,000 samples) = 54.6 MBytes 1 second PAL = (2 bytes * 35,470,000 samples) = 70.9 MBytes
So if you sample 60 minutes of an NTSC disc (one side of a CLV) you end up with about 200 Gbytes of data or 250 Gbytes for PAL.
Since (as someone pointed out earlier) the disc is pits and troughs the most important thing you get from ADC resolution is actually sensitivity across a wider peak-to-peak RF range (as the signal is weak at the beginning of a disc and strong at the end). So 10-bits was the compromise between need and cost (ADCs get a *lot* more expensive above 10-bits).
Your post here along with someone else's post would be ideal MAME FAQ material imo since it explains expected sizes of future CHD data of various laser discs. And also shows why Aaron Giles' method used in 2008 was a temporary stopgap method, but useful for showing laser disc data can also be stored in CHD at that time. Aaron's work at the time showed it was possible then.
Hopefully something regarding laser discs will be added or updated to MAME FAQ section later.
-- > Nope, assuming you agree that the criticism (that I've never agreed with, but > whatever) was that it needed to be exact (i.e. lossless) to be in MAME. > Even this approach is actually still lossy.
The previous dumps for MAME were done using loss less compression. The problem was they were made with video capture cards, which don't capture all the data on the disc. This has made it impossible to emulate some of the games.
About Laserdiscs, part 3 (errata) About Laserdiscs, part 3 About Laserdiscs, part 2 About Laserdiscs, part 1 --
I can envision laser disc owners will be grateful with your product coming to the rescue in preserving various video game laser discs. Gotta make certain that American Leisure's products such as Mad Dog McCree is preserved. :-) If that game is allowed (MAMEdev's decision) to be supported in MAME later, I'll be a happy camper.
I didn't play laser disc games in arcades myself since most of my years in arcades were prior to laser disc games appearing in arcades (1968 to 1987).
Mine was film reel based projection screen games from 1970s (used slides or film reels) whether it be Nintendo products, US Billiards etc.