D-2 (video): Difference between revisions

For other uses of the name D2, see the disambiguation page.

D2 is a professional digital video tape format created by Ampex and other manufacturers through a standards group of the Society of Motion Picture and Television Engineers (SMPTE) and introduced at the 1988 NAB (National Association of Broadcasters) convention as a lower-cost alternative to the D1 format. Like D1, D2 video is uncompressed; however, it saves bandwidth and other costs by sampling a fully-encoded NTSC or PAL composite video signal, and storing it directly to magnetic tape, rather than sampling component video. This is known as digital composite.

Ampex conceived of D2 as a more practical solution for TV Broadcasters since it could be inserted into existing broadcast chains and studio facilities without extensive redesign or modifications. This was because, among other things, in addition to its lower purchase and operating costs this D2 composite digital tape transport accepted standard RS-170A analog inputs and outputs.

Four audio channels are available for editing as well as an analog cue channel. D2 was the first digital tape format to offer "read before write" (an Ampex term) also known as "preread" on Sony recorders. Read before write allowed simultaneous playback and recording on the same VTR. For example a title could be super imposed over existing video already on the same video tape by playing the tape through a production 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 linear editing. If the digital inputs and outputs are used with a digital composite switcher multigenerational performance is excellent. Hundreds of layers of video is possible without image quality loss. Ampex D2 tape transports are extremely fast. High speed search at +/-60 times play speed with a recognizable color picture meant that you can search through three hours of videotape in just three minutes.

D2 used 19mm (¾) metal particle tape loaded into three different sized cassettes. PCM-encoded audio and timecode are also recorded on the tape. Although the D2 tapes are similar in appearance to the D1 format, they are not interchangeable.

D2 had a relatively brief heyday. As of 2003, only a handful of broadcasters use the D2 format, and even then only to access materials recorded when the format was more popular.

Panasonic's competing composite digital format is known as D3.

See also

• D3 video
• D5 HD