 Sony D-2 VCR | |
| Media type | Magnetic tape, ¾-inch |
|---|---|
| Encoding | digitalcomposite video |
| Read mechanism | Helical scan |
| Write mechanism | Helical scan |
| Standard | interlaced (NTSC,PAL) |
| Developed by | Ampex/Sony |
| Usage | Video production |
| Released | 1988; 37 years ago (1988) |
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D-2 is a professionaldigitalvideocassette format created byAmpex and introduced in 1988[1] at theNAB Show as acomposite video alternative to thecomponent videoD-1 format. It garnered Ampex atechnical Emmy in 1989.[1] Like D-1, D-2 storesuncompressed digital video on a tape cassette; however, it stores a composite video signal, rather than component video as with D-1. While component videois superior for advanced editing, especially whenchroma key effects are used, composite video was more compatible with most analog facilities existing at the time.
Ampex created the first D-2 video machine, the ACR-225 commercial spot player[2] working with Sony, who had done some early research into composite digital video,[3] as a cost-effective solution for TV broadcasters with large investments incomposite analog infrastructure such asvideo routers andswitchers, since it could be inserted into existing analog broadcast facilities without extensive redesign or modifications. This was because D-2 machines accepted standardanalog video and audio inputs and outputs. D-2 machines are capable of interfacing through eitherserial digital video or analog video connections. FourPCM audio channels are available for editing (an improvement over the then-popularType C analog machines with two audio channels) as well as an analog cue channel andtimecode, also withdigital oranalog connections.
Like D-1, D-2 uses 19 mm (¾ inch) tape loaded into three different sizedvideocassettes to supportcommercial spot playback as well as long-form programming such as movies. Although D-2 videocassette housings arenearly identical to theirD-1 counterparts, they are not interchangeable due to D-2'smetal particle tape formula, needed for its higher recording density.[2]
Ampex D-2 tape transports are extremely fast. A high speed search at 60 times playback speed with a recognizable color picture allowed three hours of videotape to be searched through in approximately three minutes.
The format uses helical scan, with an M wrap pattern in which the tape is wrapped around the head drum around the left and right side.[4] This records diagonal tracks, called helical tracks, using heads mounted on the drum which rotates at high speed. Both audio and video are recorded on the helical tracks.[5]
The D-2 offeredread before write orpreread functionality, which allowed simultaneous playback and recording on the same transport.[6] For example, a title could be superimposed over existing video already on the same video tape by playing the tape through avideo switcher, adding the title, and recording the new composite image back onto the same location of the tape. This eliminated the need for an additional recorder and saved considerable time in video editing. Steven Fuiten was the first PreRead Editor to composite video using a full D2 digital system.[citation needed]
During its early stages, finished episodes ofSouth Park were hastily recorded to D-2 to be sent toComedy Central for airing in just a few days' time.[7] D-2 replacedType C videotape for the mastering ofLaserDiscs in the late 1980s.[citation needed]
D-2 was also used to send at least some episodes ofMystery Science Theater 3000 toComedy Central for playback.[8]
D-2 was in widespread use for some ten years, as the computer-basedvideo server (with fewer moving parts and correspondingly greater reliability) became available not long after its release. By 2003, only a handful of broadcasters continued to use the D-2 format, and even then only to access materials recorded on the format.[citation needed]
Panasonic introducedD-3 in 1991; it is very similar to D-2 as it uses a smaller cassette case.
