IBM defines optical storage as "any storage method that uses a laser to store and retrieve data from optical media." '' Britannica'' notes that it "uses low-power laser beams to record and retrieve digital (binary) data." Compact disc (CD) an ...
, constant linear velocity (CLV) is a qualifier for the rated speed of an
optical disc drive
In computing, an optical disc drive is a disc drive that uses laser light or electromagnetic waves within or near the visible light spectrum as part of the process of reading or writing data to or from optical discs. Some drives can only ...
, and may also be applied to the writing speed of recordable discs
. CLV implies that the
In physics, angular velocity or rotational velocity ( or ), also known as angular frequency vector,(UP1) is a pseudovector representation of how fast the angular position or orientation of an object changes with time (i.e. how quickly an objec ...
) varies during an operation, as contrasted with CAV
modes. The concept of constant linear velocity was patented in 1886 by phonograph pioneers
Chichester Alexander Bell (1848–1924) was an American chemist and inventor. He was a first cousin of Alexander Graham Bell, and instrumental in developing improved versions of the phonograph.American History MuseumCharles Sumner Tainter Paper ...
and Charles Tainter
The LaserDisc (LD) is a home video format and the first commercial optical disc storage medium, initially licensed, sold and marketed as MCA DiscoVision (also known simply as "DiscoVision") in the United States in 1978. Its diameter typical ...
s, the first consumer optical discs, used constant linear velocity to double playback time (CLV / "extended play" discs can hold 1 hour per side; CAV / "standard play" discs can only hold 30 minutes). As the motor's speed decreases from 1,800 to 600 rpm when the read head moves away from the center (which is the start of the recording), the disc moves past the read head at a constant speed.
Later optical formats such as the audio CD
also employ CLV to maintain both a constant data rate and a constant bit density. Their rotation gradually decreases from 495 to 212 rpm to keep the disc moving past the read laser at (assuming 1:1 playback speed and Red Book encoding).
To accommodate the higher data transfer rates and random access requirements of modern
A CD-ROM (, compact disc read-only memory) is a type of read-only memory consisting of a pre-pressed optical compact disc that contains data. Computers can read—but not write or erase—CD-ROMs. Some CDs, called enhanced CDs, hold both compu ...
systems are used. This is because seek performance would be greatly affected during random access by the requirement to continually modulate the disc's rotation speed to be appropriate for the read head's position.
In case of a 12 cm standard diameter disc, data at the inner edge of the so-called ''program area'', the area containing the data (2.5 cm from disc center) is accessed at 2.4 times the angular (rotation) speed of the disc compared to at the outer edge (6 cm from disc center).
[''FUNDAMENTOS DE HARDWARE.'' – Page 37 of 45 (graphic)]
For a miniature disc with a diameter of 8 cm (radius of 4 cm), the angular (rotation) speed ratio of outer to inner data edge is 1.6 if accessed at a constant linear velocity.
This means that, for example, at a constant linar velocity of ×10, the equivalent
In physics, angular velocity or rotational velocity ( or ), also known as angular frequency vector,(UP1) is a pseudovector representation of how fast the angular position or orientation of an object changes with time (i.e. how quickly an objec ... of the disc is ×24 while the being accessed at the inner data area, while being ×10 during access at the outermost edge.
Zoned Constant Linear Velocity
Zoned Constant Linear Velocity (''ZCLV'' or ''Z-CLV'') is a modification of CLV for high speed CD and
A DVD recorder is an optical disc recorder that uses optical disc recording technologies to digitally record analog or digital signals onto blank writable DVD media. Such devices are available as either installable drives for computers o ...s where a constant linear velocity is maintained until the next zone, when the speed is stepped up. Early model recorders were CLV drives. The recording speed on such drives was rated in multiples of 150 KiB/s; a 4X drive, for instance, would write steadily at around 600 KiB/s. The transfer rate was kept constant by having the spindle motor in the drive vary in speed and run 2.4 times [ as fast when recording at the inner rim of the disc as on the outer rim. Some high-speed recorders use the zoned CLV method (ZCLV), which divides the disc into stepped zones, each of which has its own constant linear velocity. When the current zone is finished and the next zone is reached, the disc rotation will speed up, usually to the same angular speed as at the beginning of the previous zone.
At higher speeds, ZCLV offers a compromise between CAV, which enables faster ] seek time Higher performance in hard disk drives comes from devices which have better performance characteristics. These performance characteristics can be grouped into two categories: access time and data transfer time (or rate).
The ''acces ...s, and CLV, which enables greater writing reliability. A ZCLV recorder rated at "52X", for example, would write at a 52X disc rpm on the innermost zone and then progressively step down to 20X disc rpm at the outer rim to keep the rate at which bits are recorded by the laser within a narrow range. [QPxTool glossary – Zoned CLV]
This method is used for higher-speed CD-RW variants due to the narrow writing speed range of rewriteable media.
Optical Storage Technology Association
The Optical Storage Technology Association (OSTA) was an international trade association formed to promote the use of recordable optical data storage technologies and products. It was responsible for the creation and maintenance of the Universal ... – Section: Zoned Constant Linear Velocity (ZCLV)
Constant Angular Acceleration
Constant Angular Acceleration (CAA) is a variant of CLV that is used on the
The LaserDisc (LD) is a home video format and the first commercial optical disc storage medium, initially licensed, sold and marketed as MCA DiscoVision (also known simply as "DiscoVision") in the United States in 1978. Its diameter typical ... format. The initial specification of CLV (as it applies to laserdisc) results in several playback artifacts to be present in the audio/video portion as well as compatibility problems with Laserdisc players as produced by different manufacturers.
In the mid 1980s, Pioneer Electronics introduced the CAA scheme where the speed in rotation of the Laserdisc was lowered in steps and eliminated most playback artifacts and compatibility problems. Since its introduction, most manufacturers of Laserdiscs adopted the CAA format but still referred to their CAA-encoded product as CLV.
* Constant angular velocity (CAV)
* Zone bit recording (ZBR/ZCAV)
* Olivetti "personal computer" diskette format utilizing CLV with FM
Sirius Systems Technology was a personal computer manufacturer in Scotts Valley, California. It was founded in 1980 by Chuck Peddle and Chris Fish, formerly of MOS Technology and capitalized by Walter Kidde Inc. In late 1982 Sirius acquired Vict .../ Victor 9000
The name Victor or Viktor may refer to:
* Victor (name), including a list of people with the given name, mononym, or surname
Arts and entertainment
* ''Victor'' (1951 film), a French drama film
* ''Victor'' (1993 film), a French shor ... diskette format utilizing ZCLV, ZBR with GCR
Rotating disc computer storage media
Optical computer storage