CompuServe Thread

CDROM Forum · Drives/Hardware

#Single-session PhotoCD

5 messages in this thread

#46376From: Apr 20, 1993 11:57 AM

The CD-ROM article I wrote for Compuserve Magazine a couple of months ago contained a piece of bad advice. I said that the only advantage to a multisession drive was that you could send it back to the lab to add more PhotoCD scans. In fact, it turns out that (at least at some labs) even the scans from a single roll may result in a disc with more than one session. Consequently, if you want to use PhotoCDs, you really need a multisession drive.

#46543From: Todd CarterApr 21, 1993 5:55 PM

Robert: I have one of the single-session drives. What do the multi-session drives have that mine doesn't that allows those to view CD-ROMs that have multiple sessions on them? Just curious. I always like to know about what I don't have. :> Todd

#46595From: Roger C. PaoApr 22, 1993 1:12 AM

The drive has the capability of returning the location of the last Primary Volume Descriptor (PVD). On a single-session CD-ROM drive, it expects the PVD at 2:10 for all data discs. A multi-session CD-ROM drive has the ability to look for PVDs at locations other than 2:10. You can consider the PVD equivalent to DOS' FAT. It tells MSCDEX where a particular file actually is on the disc. rp93

#46652From: Apr 22, 1993 3:27 PM

FAT is a good analogy. A multisession disc is sort of like a hard drive that's been partitioned into multiple logical drives. There's no mechanical difference between single-session and multisession CD-ROM drives, just the software instructions necessary to handle Kodak's multisession spec. That's why some drives can be upgraded to multisession compatibility via a firmware ROM swap.

#46713From: Bob Banasik<BestPhoto>Apr 23, 1993 8:40 AM

Hi Robert. While it's true that scans from a single roll can lead to a multi-session disc at some labs (as you correctly stated), it is also important to point out that the customer *can* request a single session disc. We routinely get these requests from people who have only a single session drive. The downside is that if we make any "remakes" on the disc due to a poor scan, dust, or other mistakes, the "remade" scan will only appear on a multi-session drive. Customers using a single session drive will see the mistakes and not the corrections. Regards, Bob