D2: Кәсіби цифрлық бейнекассета форматы

Professional digital videocassette format

D 2 is a professional digital videocassette format created by Ampex and introduced in 1988 at the NAB Show as a composite video alternative to the component video D 1 format. It garnered Ampex a technical Emmy in 1989. working with Sony, who had done some early research into composite digital video, as a cost effective solution for TV broadcasters with large investments in composite analog infrastructure such as video routers and switchers, since it could be inserted into existing analog broadcast facilities without extensive redesign or modifications. This was because D 2 machines accepted standard analog video and audio inputs and outputs. D 2 machines are capable of interfacing through either serial digital video or analog video connections. Four PCM audio channels are available for editing (an improvement over the then popular Type C analog machines with two audio channels) as well as an analog cue channel and timecode, also with digital or analog connections.

Like D 1, D 2 uses 19 mm (¾ inch) tape loaded into three different sized videocassettes to support commercial spot playback as well as long form programming such as movies. Although D 2 videocassette housings are nearly identical ((except for certain identifier notches)) to their D 1 counterparts, they are not interchangeable due to D 2's metal particle tape formula, needed for its higher recording density. 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. The D 2 offered read before write or preread functionality, which allowed simultaneous playback and recording on the same transport. For example, a title could be superimposed over existing video already on the same video tape by playing the tape through a video 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.

During its early stages, finished episodes of South Park were hastily recorded to D 2 to be sent to Comedy Central for airing in just a few days' time. D 2 replaced Type C videotape for the mastering of LaserDiscs in the late 1980s. D 2 was also used to send at least some episodes of Mystery Science Theater 3000 to Comedy Central for playback. D 2 was in widespread use for some ten years, as the computer based video 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. Panasonic introduced D 3 in 1991; it is very similar to D 2 as it uses a smaller cassette case.