D-2 is a digital video tape format created by Ampex and other manufacturers through a standards group of SMPTE) and introduced at the 1988 NAB (National Association of Broadcasters) convention as a lower-cost alternative to the D-1 format. Like D-1, D-2 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.
The D-2 offered "read before write" or "pre-read" functions where you could insert over material already recorded on tape. It offered simultaneous playback and recording on the same video tape recorder.