Optical Media, Part 2
Digital Video Discs, commonly known as simply "DVDs", began to reach American consumers in the late 1990's. It was heralded as the ultimate digital video solution. Since then, DVD has replaced VHS as the medium of choice for movies and other types of videos or films.
DVDs share a great deal with their CD cousins. For beginners, both are optical media that work in circular tracks. Both are read with focused, narrow beams of light ("lasers") that bounce off a reflective layer within the disc. They also share the same physical layout and dimensions (diameter).
DVD discs, however, cannot be read by standard CD readers (computer CD drives, CD audio players, etc). A DVD reader is needed instead, which uses a higher frequency laser diode due to increased capacity (density). Luckily, DVD readers can read CDs (commercial CDs, CD-Rs and usually CD-RWs as well) with ease.
Additionally, burning or writing to DVD discs require a DVD burner (a DVD disc drive that can "write" to blank DVD discs) and DVD-burning software. CD burners don't have DVD-writing capabilities. However, nearly all DVD burners can also burn CD-R and CD-RW discs.
One unique feature of DVD discs is the fact that they are often multi-layered, which is how they achieve such high data capacities. In fact, it is not uncommon to notice a slight delay mid-way through a movie, when the player has to switch to the second layer. Early DVD drives which were only capable of reading single layer DVD discs would fail when the reader reached the end of the first layer.
Contrary to their name, DVD discs can also be used to store data files, in addition to movies and even audio. In fact, DVD discs are becoming a very popular data storage medium because of their high data storage capacities that can range from 4.7 gigabytes (GB) to 17 gigabytes (GB). Newer, emerging standards have capacies that are in excess of 30 gigabytes (GB).
Unfortunately, the DVD disc has some pitfalls. For starters, there are several DVD disc types - DVD-R, DVD+R, DVD+RW and DVD-RAM, not to mention the newly introduced HD-DVD and Blu-ray DVDs which are just barely starting to creep onto the market. Not all readers (disc drives, players) can play all these different DVD discs. Thus, there is no single DVD standard, like there is with CDs.
Customer confusion is common, as one might imagine. Many will recall the VHS versus Betamax competition and the confusion that ensued. In many ways, however, the current DVD situation is worse because of the myriad disc types and the subtle differences in names. For example, "DVD-R" and "DVD+R" are entirely different types of DVD discs.
Most recent DVD readers (including players and computer disc drives) can read DVD-R and DVD+R discs. However, HD-DVD and Blu-ray are entirely different, and it is unlikely that a drive will be produced which can read both, in addition to the older DVD-R and DVD+R standards.
On the bright side, HD-DVD and Blu-ray DVD discs will bring higher storage capacities and greater multimedia capabilities. Either type will be able to hold a great deal more than traditional DVD discs.
Like CD-R discs, files, photos, videos or audio burned to a DVD-R and DVD+R disc cannot be removed, deleted or erased. However, if there is remaining space on the data disc, additional files can be added through the creation of additional burning sessions. Most DVD-burning software will add this session for you. As with CD-R data discs, DVDs require that sessions be closed before the data within that session can be read. Once a session is closed, it cannot be re-opened or added to.
DVD-RW and DVD-RAM discs behave much like CD-RW discs in that they can be erased and re-used. Like CD-RW discs, expect slower write/burning times.
Burning video to a DVD disc, so that it plays like a commercial DVD movie is possible, but complicated and beyond the scope of this article. It does require special software and isn't as easy as burning audio to a CD.
In any event, DVDs are here to stay, and aren't going to fade away any time soon!
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