The Subtle Differences

Continued from previous page Did you know?
DVD discs do not wear out and are unaffected by magnetic fields (which can literally erase a VHS cassette).

The Two Different DVD Disc Formats

The two main types of recordable DVD media are called DVD-RW ("dash" RW) and DVD+RW ("plus" RW). As per the organization called “DVD Forum”, the DVD+RW and DVD+R officially do not belong to the DVD family. Another recordable format worth mentioning is called DVD-RAM, and it first appeared in the late '90s, but it has been rather unpopular due to the general lack of compatibility with set-top DVD players.

For more information on various types of DVD disc formats go here: http://www.disctronics.co.uk/technology/dvdintro/dvd_formats.htm

There is also a very detailed PDF document here: http://www.itl.nist.gov/div895/carefordisc/CDandDVDCareandHandlingGuide.pdf

Did you know?

All recordable DVD media have a microscopic wobbled groove embedded in them. The “wobble” gives the recorder the timing information it needs to record the data accurately. Pressed DVDs (pre-recorded and not recordable) do not have this wobbled groove as they do not need it.

The characteristics of DVD-RW ("dash” RW):
- developed by Pioneer, for recording DVDs for home use
- initially "write once" (DVD-R)
- first consumer format compatible with most set-top DVD players
- up to 1,000 rewrites
- linear (sequential) data format (meaning: single, continuous stream)
- lacks random-access capability
- lacks native defects management
- relatively inexpensive
- media types: "A" for Authoring (professional use, requires expensive recording equipment with a different kind of laser), and "G" for General use

The characteristics of DVD+RW ("plus” RW):
- developed by the “DVD+RW Alliance” (Dell, Hewlett-Packard Company,
MCC/Verbatim, Philips Electronics, Ricoh Company Ltd., Sony Corporation, Thomson multimedia and Yamaha Corporation)
- has many characteristics of DVD-RW
- initially dubbed "the compatible, rewritable DVD format"
- up to 1,000 rewrites
- can be formatted as sequential data streams (video) or random-access (similar to DVD-RAM technology)
- compared to DVD-RW, the DVD+RW incorporates a higher frequency wobble in the embedded microscopic tracking groove
- "lossless linking technology" (the recorder can stop and start the writing process with extreme accuracy)
- good defect management ensures data read / write accuracy
- more expensive, and distributed by fewer vendors

From the above, you can see that the differences are there but they are not something you need to really worry about. For the "General use" (your videos, audio or data backups), the readily available DVD-R/-RW will do just fine.

Please note: The CSS (copyright) protected content cannot be written to any of these discs.



Special thanks to guest author, Joanna Gurnitsky, for this meticulously-researched article.

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