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In optical storage, constant angular velocity (CAV) is a qualifier for the rated speed of an optical disc drive, and may also be applied to the writing speed of recordable discs. A drive or disc operating in CAV mode maintains a constant angular velocity, contrasted with a constant linear velocity (CLV).
When playing back music, a compact disc (CD) employs CLV to maintain a constant data rate. The motor speed decreases from 495 to 212 rpm as the read head moves away from the center to keep the disc moving past the read head at a constant linear velocity.
High speed CD and DVD drives use CAV.
CAV was used in the LaserDisc format for interactive titles, as well as special editions of certain films. CAV allowed for perfect still frames, as well as random access to any given frame on a disc. Playing time, however, was cut in half from 60 minutes to 30 minutes.
CAV is used with Nintendo GameCube Game Disc and Wii Optical Disc, as well as the Sega GD-rom.
