Quadruplex videotape
A reel of 2-inch quad videotape compared with a miniDV videocassette
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| Media type | Magnetic Tape |
|---|---|
| Encoding | NTSC, PAL |
| Developed by | Ampex |
| Usage | Video production |
2-inch quadruplex videotape (also called 2″ quad, or just quad, for short) is the first practical and commercially successful analog recording videotape format. It was developed and released for the broadcast television industry in 1956 by Ampex, an American company based in Redwood City, California. The first videotape recorder using this format was built and created in the same year. This format revolutionized broadcast television operations and television production, since the only recording medium available to the TV industry before then was film used for kinescopes, which was much more costly to utilize and took time to develop at a film laboratory. In addition, kinescope images were usually of obviously inferior quality to the live television broadcast images they recorded, whereas quadruplex videotape preserved almost all the image detail of a live broadcast.
Since most United States West Coast network broadcast delays done by the television networks at the time were done with film kinescopes that needed time for developing, the networks wanted a more practical, cost-effective, and quicker way to time-shift television programming for later airing on the West Coast. Broadcasters also sought a recording medium that was not as costly or time-consuming to edit and develop as film. Faced with these challenges, broadcasters sought to adapt magnetic tape recording technology (already in use for recording audio) for use with television as well.
The name "quadruplex" refers to the use of four magnetic record/reproduce heads mounted on a headwheel spinning transversely (width-wise) across the tape at a rate of 3,600 (for 14,400 recorded stripes per second) rpm for NTSC 525 lines/30fps-standard quad decks, and at 3,750 (for 15,000 stripes) rpm for those using the PAL 625 lines/25fps video standard. This method was called quadrature scanning, as opposed to the helical scan transport used by later videotape formats. The tape ran at a speed of either 7.5 or 15 in (190.5 or 381.0 mm) per second for NTSC 525/30 video recording, or 15.625 in (396.875 mm) per second for PAL 625/25 video; the audio, control, and cue tracks were recorded in a standard linear fashion near the edges of the tape. The cue track was used either as a second audio track, or for recording cue tones or time code for linear video editing.
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