ok this article is taken from dvd+r digest
here >
http://www.dvdr-digest.com/articles/articles.php?article_id=4&mode=print
all credits are to :-
Honda Shing, CTO of Intervideo
for this article that explains the differences in standards of dvd blank media's
********************************
Don't Be Stumped By DVD Standards
Author: Honda Shing, CTO of Intervideo
Last Updated: Mar 05, 2002
DVD is the hottest thing to hit consumers, well, ever. Consumers are snatching up DVD movies like "Shrek" in record numbers, and even moribund TV series like "Twin Peaks" and "M*A*S*H" are finding new life as DVDs. Home DVD players are selling at a faster rate than the radio, Internet or even television was adopted. Virtually all new computers come with a DVD drive allowing tens of millions of consumers the ability to play DVDs on a computer. But the biggest change is yet to come. 2002 is the year a number of manufacturers have, or will, release DVD burners, allowing consumers the ability to make their own DVDs with a computer for the first time ever. However, intrepid DVD creators should proceed with caution. DVD is a new technology and not all devices support the same standard. In fact, there are a number of competing formats for making your own DVDs making it possible that the DVD you create on your computer may not play in your living room. This article will arm you with the information you need to know to keep that from happening. But pay close attention, in a moment the acronyms are going to start flying around like a box of nails caught in a tornado.
The easiest way to understand the subtleties of DVD technology is to divide the discussion into 3 parts: application formats, writable formats and DVD drives.
Let's begin with application formats. The good news is that every DVD movie that you buy or rent is in a single application format called DVD-Video. All DVD players and DVD drives can play DVD-Video. Now the bad news, you might create your own DVD-Video movie and it might not play in your DVD player. Sounds odd, doesn't it? Let's move on to writable formats. Although DVD disks look like CDs, they are not the same thing. The biggest difference is that a DVD can hold much more information than a CD. Most CDs hold 650 or 700 megabytes of data, movies or music. Most DVDs hold 4.7 gigabytes, or about 7 times more information than a CD. This extra capacity allows entire Hollywood movies to fit on a single disk. If you want to create your own DVD movie, you will need to get a writable version of one of these DVD disks. This is where it starts to get complicated.
Imagine if there were 5 different kinds of VHS tapes and they all looked identical but were not that is basically where the DVD standards world is right now. There are essentially 5 versions of writable DVD that you need to understand. They are: DVD-R, DVD-RAM, DVD-RW, DVD+RW and DVD+R. The distinctions are actually based on how the data is written to and read from the disk, and this differentiation is difficult to translate to the physical world, however one example might be language.
Imagine if the entire world agreed on a single language for all written documents, say English. In the United States we would continue to create English documents and books in which one reads left to right. But another country might prefer to write and read English right to left. And yet another, top to bottom, and so on until the effect became that although all documents were created in a single language, it would be very difficult for a person from one country to read a document from another country. DVD recording is in a similar state of confusion. DVD is such a nascent technology that these issues have yet to work themselves out, so you have no choice other than understanding them all. One easy way to think about the formats is as 5 completely different kinds of DVD disks.
First, let's divide the formats up. The first thing to note is that DVD-R and DVD+R disks can only be recorded once. You only get one chance to record your DVD movie to this kind of disk It's like pouring cement, once it is done you'll need to destroy it to change it. Further, DVD-R discs come in 2 types: DVD-R(A), for "authoring," and DVD-R(G), for "general." Both DVD-R and DVD+R discs will play in most DVD players, even older ones. So if you put your movie on this kind of disk there is a high probability that it will play in your living room. However, DVD-R(A) drives can not record to DVD-R(G) disks, and vice versa.
There are also DVD formats that can be recorded more than once. DVD+RW, DVD-RW and DVD-RAM disks can all be recorded thousands of times. If you don' t like how your DVD movie turns out, you can record a new version right on the same disk. These disks are more like painting a wall, if you don't like the color you just put on a new coat.
Each of these rewritable formats are a little different. DVD-RAM, for instance, was created for storage of computer data like backing up your hard drive. If you want to get a DVD writer to back up computer data, DVD-RAM is a solid option. However, if you plan to make your own DVD movies, one of the other formats may be better suited for that activity. Most DVD players can't play DVD-RAM disks.
The DVD-RW and DVD+RW formats are both good for making DVD movies but are essentially engaged in a Beta versus VHS-type battle. The consumer market will ultimately determine which format wins or they end up combining into a single standard, but it is important to understand that neither is yet a universal standard. Another thing to note is that many DVD players won't play any kind of rewritable disk. Most of the newer players will play these kinds of disks, but if you have an older DVD player it may not. In general, the newer your DVD player, the more likely it is to play all the recordable formats. There are web sites like Apple.com, HomeMovie.com and DVDplusRW.org that list compatible players and formats, but these are not unabridged resources either. Use them as a general guide.
That covers the basic DVD writable formats, the last point of concern is the DVD drive itself. This is the part of your computer that will actually record your data or movie onto the DVD disc. Thankfully, if you have made it this far you are almost home. The different types of DVD drives basically break down into the same formats as the DVD writable formats. Therefore, there are DVD-RAM drives, DVD-R drives etc. on down the line. It is also increasingly likely that DVD burners will come with the ability to record to more than one format, for example a manufacturer may offer a DVD+R/RW drive meaning that it can record both DVD+R and DVD+RW discs. When considering DVD media (the actual silver discs) and DVD burners, make sure that both the discs and drive are the same format.
***************************
hope this is of use to many
maby we could make this a sticky admin !?
