, showing the NTSC field setup and individual scan lines of a
LaserDisc copy of
''The Mind's Eye'' (1990), showing that the
closing credits of the film are physically visible on the disc medium itself. Because on a CAV-formatted LaserDisc the adjacent tracks encode the same line in the NTSC video signal across different frames, and because the closing credits scroll vertically at a constant rate, the signal produces a coherent image on the disc.
Gramophone records have always used CAV, including
CEDs which provide video signals. Some high-speed CD and DVD drives can use CAV. It allows for shorter
access times because the rotation speed (angular velocity) does not need to be changed when the laser seeks across the disc, similarly to the
magnetic head of a
hard disk drive. With a given angular (rotation) speed, the linear speed at the outermost track is nearly 2.4 times as fast as that of the innermost track. CAV was used in the
LaserDisc format for interactive titles; it was also used with
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 30 minutes on each side (these discs are also known as "standard play"), as opposed to 60 minutes on each side for CLV-based discs ("extended play"). CAV is used with the
Nintendo GameCube Game disc and Wii Optical disc, the
original Xbox discs, and Sega's
GD-ROM.
Partial constant angular velocity (P-CAV) If the used media (e.g.
DVD-RAM variants) has a linear (writing) speed limitation that can not be attained with physically supported angular (rotation) speeds at the inner edge of the recordable area, the disc writing can start off with a constant angular velocity, until the increasing linear velocity has reached the writing speed limitation of the disc. At that point, the drive transitions into writing with a constant linear velocity. ==See also==