The Physics
Factbook
An encyclopedia of scientific essays

# Speed of a DVD

Bibliographic Entry Result
(w/surrounding text)
Standardized
Result
Taylor, Jim. DVD Demystified. New York: McGraw Hill, 1997: 122. "scanning velocity: 3.49 m/s (SL), 3.84 m/s (DL)" 3.49 m/s
(SL)
3.84 m/s
(DL)
Nemec, Philip. A Day at the DVD Forum: technical notes. Silicon Graphics. "Reference scanning velocity, meters/sec; DVD 3.49 SL, 3.84 DL; CD 1.2 to 1.4" 3.49 m/s
(SL)
3.84 m/s
(DL)
Fogg, C. Physical Parameters. DVD Technical Notes. MPEG Pointers and Resources. 21 July 1996. "Reference scanning velocity, meters/sec; DVD 3.49 (SL), 3.84 (DL); CD 1.2 to 1.4" 3.49 m/s
(SL)
3.84 m/s
(DL)
Taylor, Jim. The Official DVD FAQ. The Digital Bits. "To compensate, the reference scanning velocity is slightly faster -- 3.84 m/s, as opposed to 3.49 m/s for single layer discs." 3.49 m/s
(SL)
3.84 m/s
(DL)

Everyone loves TV. Whether we want to admit it or not, our modern world would not exist without TV. After TV came computers, VCRs, CDs, and finally in March of 1997, US stores began to sell DVDs. Who wouldn't want to watch a movie on their own computer, or have the movie for years and years without having to worry that the quality was decreasing each time they watched it. Well, DVD gives us all that and more.

DVD stands for "digital versatile disk", or a "digital video disk". The DVD format has advantages over compact discs (CD) as well as VHS video tape. Even though a CD and a DVD are about the same size (12 cm), a DVD's capacity to store information is about six to seven times greater. This is accomplished by putting information on both sides of the DVD and adding an additional layer to each side. The transfer rate of data from a DVD can be sustained at more than one megabyte per second. Best of all, if you buy a computer with a DVD-ROM, you don't have to buy a separate CD-ROM, since you can use it for both CDs and DVDs.

The scanning velocity of a DVD is the speed at which the spiral track of a disk passes under the laser pickup head. For a single layer disk (SL), the scanning velocity is set at 3.49 m/s. For a double layer disk (DL), where two layers of information are recorded per side, it is 3.84 m/s (±0.03).

A big difference between a DVD or a CD and a phonograph record is that a DVD has a constant linear velocity. This means that the drive has to spin faster or slower depending on its distance from the center, while records have a constant angular velocity.

Bella Fridman -- 2000