(Digital VideoDisc or Digital Versatile Disc) An optical digital disc for storing movies and data. Introduced in the U.S. in 1997, and developed by both the computer and movie industries, the disc uses the same diameter platter as a CD (120mm/4.75" diameter), but holds 4.7GB rather than 700MB. Whereas CDs use only one side, DVDs can be recorded on both sides as well as in dual layers. DVD drives/players read most CD media as well. See CSS and DVD region codes.
For 2x, 4x, 8x, etc. drive specifications, see DVD drives.
Movies - Standard Definition
DVD-Video is the movie format, which uses MPEG-2 compression to provide approximately two hours of video per side at standard definition TV resolution (480i resolution). When most people mention the word "DVD," they are referring to a DVD-Video disc. See DVD-Video and DTV.
Movies - High Definition
Blu-ray is the video format that has enough storage for high-definition movies at 1080p resolution. See Blu-ray and table of capacity comparisons below.
Read-Only Data DVDs
Designed for data files, a DVD-ROM disc is a higher-capacity CD-ROM, and like CD-ROMs, DVD-ROMs are manufactured. See DVD-ROM.
Writable/Recordable Data DVDs
A DVD-RAM is a rewritable DVD that functions like a removable hard disk. DVD-RAM media can be rewritten 100,000 times before they are no longer usable. See DVD-RAM.
DVD-R and DVD+R are competing write-once formats for movies or data. DVD-RW and DVD+RW are competing rewritable (re-recordable) formats that unlike DVD-RAM's 100,000 cycles, can only be rewritten 1,000 times. Aimed at the consumer, 1,000 rewrites is considered more than sufficient. See DVD-R, DVD+R, DVD-RW and DVD+RW.
Music DVDs
DVD-Audio is a second-generation digital music format that provides higher sampling rates than audio CDs. Many welcomed the new format, believing that the original audio CD was unable to capture the total sound spectrum, but it never took off. See DVD-Audio.
DVD Stands For?
Originally, "Digital VideoDisc." Since the technology became important to the computer world, the "video" was dropped, and it was just D-V-D. Later, it was dubbed "Digital Versatile Disc" by the DVD Forum. Take your pick.
Minus (-R/-RW) and Plus (+R/+RW)
The formats endorsed by the DVD Forum (www.dvdforum.org) have a hyphen in their names and are verbalized as "DVD Minus R" or "DVD Dash R" (DVD-R) and "DVD Minus RW" or "DVD Dash RW" (DVD-RW). The competing formats from the DVD+RW Alliance (www.dvdrw.com) use a plus sign: "DVD Plus R" (DVD+R) and "DVD Plus RW" (DVD+RW). Starting in 2002, drives that supported both Minus and Plus formats were introduced. See DVD Forum and DVD+RW Alliance.
Specifications
Following are the various DVD types and capacities. Also included is the Blu-ray high-definition format (see Blu-ray). See also DTV.
Type Sides Layers Capacity
Read Only Standard Definition
DVD-Video/DVD-ROM 1 1 4.7GB (DVD-5)
DVD-Video/DVD-ROM 1 2 8.5GB (DVD-9)
DVD-Video/DVD-ROM 2 1 9.4GB (DVD-10)
DVD-Video/DVD-ROM 2 2 17.0GB (DVD-18)
Read Only High Definition
Blu-ray (BD-ROM) 1 1 25.0GB
Blu-ray (BD-ROM) 1 2 50.0GB
Blu-ray (BD-ROM) 2 1 50.0GB
Write Once Standard Definition
DVD-R (A) 1 1 4.7GB
DVD-R (G) 1 1 4.7GB
DVD-R (G) 2 1 9.4GB
DVD-R DL 1 2 8.5GB
DVD+R 1 1 4.7GB
DVD+R DL 1 2 8.5GB
Write Once High Definition
Blu-ray (BD-R) 1 1 25.0GB
Blu-ray (BD-R) 1 2 50.0GB
See Blu-ray.
Type Sides Layers Capacity
Rewritable Standard Definition (100K cycles)
DVD-RAM Ver. 1 1 1 2.6GB
DVD-RAM Ver. 1 2 1 5.2GB
DVD-RAM Ver. 2 1 1 4.7GB
DVD-RAM Ver. 2 2 1 9.4GB
DVD-RAM (80 mm) 1 1 1.46GB
DVD-RAM (80 mm) 2 1 2.92GB
Rewritable Standard Definition (1K cycles)
(Also called "Re-recordable")
DVD-RW 1 1 4.7GB
DVD-RW 2 1 9.4GB
DVD+RW 1 1 4.7GB
DVD+RW 2 1 9.4GB
Rewritable High Definition (10K cycles)
Blu-ray (BD RE) 1 1 25.0GB
Blu-ray (BD RE) 1 2 50.0GB
See Blu-ray.
Sides and Layers
DVDs come in any combination of single or double sided with single or double layers. This shows the laser beam contacting the recorded surface in all of the possibilities.
DVD Vs. CD-ROM
At minimum, the capacity of a DVD is seven times that of a CD-ROM because its tracks, pits and lands are more than twice as dense. It also uses more efficient recording algorithms. Add a second layer or record on both sides of the DVD, and capacity is doubled. (Image courtesy of C-Cube Microsystems.)
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