D-2 is an early 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. Like D-1, D-2 stores uncompressed digital video on a tape cassette; however, it stores a composite video signal, rather than component video as with D-1. While the component video is superior for advanced editing, especially when chroma key effects are used, composite video is more compatible with most existing analog facilities.
ampex created the first D-2 video machine, the ACR-225 commercial spot player 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 to their D-1 counterparts, they are not interchangeable due to D-2's metal particle tape formula, needed for its higher recording density.
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 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 had a relatively brief heyday, as the computer-based video server (with far fewer moving parts and correspondingly greater reliability) became available soon after its release. In 2003, only a handful of broadcasters continued to use the D-2 format, and even then only to access materials recorded when the format was more popular.
panasonic's competing composite digital format is known as D-3.