Okay, now I've gone from ignorant to partially enlightened to confused.
Iggy, you say that the reader determines if a disk is OTP or PTP? Or do you mean something else? Could you clarify?
I would think that the media--even a 'blank' +R DL disc--would be predetermined to be OTP or PTP by the nature of the 'pregrove', right? I'm a little vague on how DVD works at a very low level. I'm fairly knowledgable of the low levels of CD-R media, and I make the assumption that DVD is similar. Speaking of which is there a good tutorial on that?
The DVD-ROM that I have is a Microsoft Developers disc, so it's purely data, maybe that's why they pressed it PTP? Most other 'DVD-ROM' disks that I've seen are really DVD-Video with some computer content, so, for the sake of the video, they're OTP.
I'd still like to know why there are both kinds. If we have to have OTP for Video, why even bother with having a PTP standard--unless there's something useful about it. Like being cheaper to master/press or better seek time in a DVD-ROM drive, etc.