writable DVD: A GUIDE FOR THE PERPLEXED

Emedia Professional, Jan, 1999 by Dana J. Parker

Applications

Q: If I had a DVD-R or DVD-RAM or DVD RW drive, could I use it to copy DVD read-only discs?

A: If the read-only disc is not copy protected, if its capacity is less than one side of the media you are recording to, and if you have the necessary software, yes.

Q: How can I make a complete backup from a Original DVD into a DVD-R drive (of a DVD-Video movie)?

A: You can't, if the movie is copy protected, and most are. Also, DVD-R media is currently only 3.9GB per side--pressed DVD single layer is 4.7GB per side.

Q: Can I do any backup in a DVD-RAM unit?

A: Sure, you could back up your hard drive or copy a CD. You can't copy a movie that is copy-protected.

Q: Can I use DVD-RAM to create my own DVD discs?

A: Yes--you can create a disc in the DVD logical and application level format (DVD-Video, DVD-ROM).

Q: Advocates of DVD RW (or maybe it was DVD-R/W) are talking about caddyless disks. What does that mean exactly?

A: People prefer bare discs. The question of whether to use caddyless media was a point of some contention in deciding on the DVD read-only specs, and the decision was to make the format like CD--bare disc (incidentally, most early CD-ROM drives required caddies). The recommendation of the rewritable DVD technical working group was also for a bare disc. DVD-RAM uses an "optional" cartridge (not a caddy), and it's the only DVD format that does, because the media is more susceptible to being damaged by handling than the others.

Q: Are there yet other formats that have been announced? And do they all promise to be backwards-compatible with all the same formats other than the competing rewritable DVD ones?

A: Yes, there are MMVF and ASMO, whose specifications have been announced, but whose supporters have not released any updates on their development in over a year.

None of the media defined by the rewritable high-density removable optical formats (called DVD or not) are completely compatible with existing hardware. All of the specified drives, however, will be able to play pressed DVD discs. Whether they can play DVD-Video or not depends on whether there is a decoder in the system. Whether they can play CD, CD-R, or CD-RW depends on the manufacturer.

Q: DVD-RAM media can be two-sided, and using both sides you have a total capacity of 5.2GB--more than enough for storing the content of your new 4.7GB DVD-ROM masterpiece on its way to the replicator. What am I missing here?

A: For starters, the fact that DVD mastering machines aren't set up to accept DVD-RAM as input. One reason is the capacity--you'd have to make two images, one for each side, and then have the mastering facility splice them together into a single image on DLT. For logical reasons, this is not advantageous--an application requiring over 2.6GB of capacity could not be tested as a whole, and it could not be tested in an actual DVD-Video player. DVD-RAM is not targeted at beta testing and authoring applications.

Q: Which is better, DVD-RAM or DVD-RW?

A: It all depends on what you want to use it for. Think of it as making a choice between a big CD-RW and a big PD.