Confused about the plethora of DVD-writeable formats on the market? Our Australian Tech Guide will explain everything you need to know about DVD-R/RW, DVD+R/RW and DVD-RAM.

What formats are available for DVD writing?
Currently, there are three major DVD-writeable formats: DVD-R/RW, DVD+R/RW and DVD-RAM.

What's DVD-R/RW?
DVD-R/RW is the DVD-writeable/rewriteable format of the DVD Forum, which sets the 'official' standards for DVD media. DVD- discs tend to be a touch cheaper than their positive cousins. At the time of writing, you could expect to pay around AU$10-$15 for a single disc, with prices getting cheaper for bulk purchases.

DVD-RW DVD-R/RW discs come in two different sub-flavours as well, although unless you're in the professional video production business, you're unlikely to come across DVD-R Authoring (DVD-R(A) ) discs. Consumer DVD-R/RW discs use DVD-R (General) media, which uses a 650nanometer laser to write to each disc in essentially the same way that a CD-R/RW drive does. DVD-R/RW(G) discs are created with inbuilt copyright protection measures to make it (theoretically) impossible to duplicate copyrighted video content, although that's something that's rather easy to bypass. Many DVD-R/RW drives will also at least read DVD-RAM discs, and some will write to them as well.

What's DVD-RAM?
DVD-RAM is the oldest of the recordable DVD formats, at least in terms of available consumer products. Originally envisioned as a computer storage medium, the first DVD-RAM discs came encased in individual plastic caddies to protect the discs -- not a bad idea on the surface, but not one that really caught on. With an emphasis on computer use, DVD-RAM is also theoretically more robust and should stand up to around 100 times more write and rewrite cycles than DVD-RW or DVD+RW. We don't quite have the patience to do 100,000 rewrites of a 4.7GB disc, but if you're not doing anything for the next few years, let us know how you got on.

DVD-RAM should probably have been superseded by DVD- and DVD+ formats, but has seen something of a renaissance and is being used by some manufacturers for home DVD Recorders and digital cameras. As it's a format that was built around computer use, it has good defect management and rapid disc access. This makes it quite suitable for home recording use, with one major caveat; the vast majority of home DVD players won't read DVD-RAM discs. For this reason, DVD-RAM home recorders tend to be able to write to DVD-R as well.

What's DVD+R/RW?
DVD+R/RW is the black sheep of the DVD-writeable pack, as it's not an official DVD Forum standard, despite being designed by several of the member companies of the forum, calling themselves the DVD+RW Alliance. DVD+RW offers the same kind of fast access and incremental rewriting of DVD-RAM without the incompatibility problems that format has. Generally speaking, both the media and drives for the +R/+RW format are more expensive than their -R/-RW brethren, partly due to the technology simply being newer. Unlike DVD-R/-RW, the DVD+ format started out with the +RW format first; it took more than a year for +R to make its grand appearance. A single DVD+RW disc should cost you approx AU$20.

So which is more compatible with my DVD player/DVD-ROM drive?
At this stage, that's a 'how long is a piece of string' question. Depending on whose PR spin you read, either DVD-R/RW or DVD+R/RW is more compatible with consumer DVD-ROM drives and DVD players than the competing format. The DVD Forum has approved a standard and logo for players compatible with DVD-R/RW and DVD-RAM, known as DVD-Multi. If you have a drive/player with the DVD Multi logo on it, then it should (in theory) be able to handle those discs. Meanwhile, the DVD+RW Alliance likes to claim a higher rate of acceptance in non-burning drives for the +RW format, on the grounds of the technical specifications being written with video creation in mind. Several of the more recent home DVD players will indicate, either on the player or on the box, if they support DVD- or DVD+ formats.

It gets more complicated than that, though. Just because you have a player or drive that should accept a burnt DVD doesn't mean it necessarily will. Just like with CD-R/RW, the quality of the media you use and even the circumstances surrounding how a disc was burnt can affect whether your particular drive will accept it. It's literally a 'try it and see' scenario. One way to increase your odds would be to read burnt discs in a DVD-/+R/RW writer; a drive that can burn discs in whatever format you have will usually read them as well, and with fewer fault-tolerance issues.

Generally speaking, if your main priority is cross-drive compatibility, you'll be better off with write-once -R or +R discs; their reflectivity pattern is closer to that of commercially-pressed discs, and so more drives tend to accept them. -RW/+RW discs are becoming more common, and over time it's likely that the compatibility rates will rise across all media.

So which format should I invest in?
The battle between the 'official' -R/RW and rogue +R/RW formats is far from over. Unless all you're going to be doing is burning data, we wouldn't recommend a DVD-RAM drive, especially as the discs can generally only be read by other DVD-RAM drives. Sony's had a reasonable amount of success with its DRU-500A drive, which records both - and + DVD media, although whether that's a model that future drives will copy is a little uncertain at the moment.

In pure technical terms, DVD+R/RW has advantages over DVD-R/RW, but as with anything in IT, it's not always the best solution that wins out in the end.

Can I use a DVD burner to copy movies?
That's the AU$250,000 question -- at least, that's how much you could be fined if you're talking about copying commercial material. The short technical answer, however, is that it is possible, as long as the content you're copying is small enough to fit onto a single sided 4.7GB disc. Many commercial DVDs run longer than this, especially with extras, or are dual-layered discs with an overall higher capacity. There are a variety of ripping tools that can down-sample a longer DVD to fit under the 4.7GB barrier, although as with any downgrading, you won't end up with a DVD-quality copy.