Contrast With Quadruplex Recording
Helical scanning was a logical progression beyond an earlier system (pioneered by Ampex) known as quadruplex recording, also referred to as transverse recording. In this scheme, the rotating head drum ran essentially perpendicular to a 2-inch-wide (51 mm) tape, and the slices recorded across the tape were nearly perpendicular to the tape's motion. U.S. quadruplex systems revolved the head drum at 14,400 revolutions per minute (240 revolutions per second) with four heads on the drum so that each television field was broken into sixteen stripes on the tape (which required appropriately complex head-switching logic). By comparison, the longer stripe recorded by a helical scan recorder usually contains an entire TV field and the two-headed head drum spins at the frame rate (half the field rate) of the TV system in use.
Recording an entire field in a single pass allowed these machines to play back a viewable still frame when the tape was stopped, and display a viewable image sequence while shuttling forwards or backwards. This greatly facilitated the editing process. The quadruplex systems were unable to display video from tape except while playing at normal speed.
Read more about this topic: Helical Scan
Famous quotes containing the words contrast with, contrast and/or recording:
“Happiness ain’t a thing in itself—it’s only a contrast with something that ain’t pleasant.... And so, as soon as the novelty is over and the force of the contrast dulled, it ain’t happiness any longer, and you have to get something fresh.”
—Mark Twain [Samuel Langhorne Clemens] (1835–1910)
“Happiness ain’t a thing in itself—it’s only a contrast with something that ain’t pleasant.... And so, as soon as the novelty is over and the force of the contrast dulled, it ain’t happiness any longer, and you have to get something fresh.”
—Mark Twain [Samuel Langhorne Clemens] (1835–1910)
“Self-expression is not enough; experiment is not enough; the recording of special moments or cases is not enough. All of the arts have broken faith or lost connection with their origin and function. They have ceased to be concerned with the legitimate and permanent material of art.”
—Jane Heap (c. 1880–1964)