D1 (Digital component). Developed by Sony, this was the first high quality digital VTR format. It is still used for television commercials post produced on videotape, following a high quality digital telecine transfer from 35mm negative film. D1 VTRs are extremely expensive which is why they are not generally used in broadcast work.- D2 (Digital composite). Marketed by Sony and Ampex, D2 looked set to be the standard replacement for 1" tape throughout the industry. In the UK, however, it was only adopted by a few of the ITV companies and has now itself been superseded.
D3 (Digital composite). Developed by Panasonic, this format offered similar quality and features to D2 but on a narrower width tape. This format was adopted by some companies, including the BBC, as a replacement for 1".- D5 (Digital component). Another Panasonic format, D5 is a component version of D3. D5 machines can handle pictures in the widescreen 16 9 ratio and can also replay D3 tapes. In the UK, Channel 4 has adopted D5 as its transmission format.
- Digital Betacam (component). A digital version of Betacam which can also handle 16 9 widescreen pictures. Some machines can replay analogue Betacam SP and Betacam tapes; however, no digital Betacam machines can record in analogue Betacam SP. The growth of Digital Betacam is fast making it the universal high-end format.
digital (DVCam, DVCPro, MiniDV). A family of digital formats supported by a number of manufacturers, DV can range from domestic quality (although digital), to a broadcast quality which is the digital equivalent of BetaSP. Although MiniDV tapes can be played back in most machines, DVCam and DVCPro normally require dedicated equipment.
The simplest way to understand the difference between analogue and digital is to think of a domestic audio cassette tape and a compact disc. The audio cassette is an analogue recording and the compact disc is a digital one. The CD gives spectacularly better quality. Digital video recording gives a similar improvement when compared to analogue video recording.
All of the new formats developed in the last few years have been digital rather than analogue. Apart from higher quality, the main advantage of digital VTRs is that there is minimal loss of quality when pictures are copied, as in editing, compared to analogue VTRs. In addition, many digital VTRs offer a facility known as read-before-write or pre-read, which means you can replay an existing picture off a VTR at the same time as replacing it with a fresh one. This is especially useful in editing applications involving complex multi-layering, but is best explained by the example of adding name superimpositions to an already edited programme using one machine only. The image is replayed (read) off the machine, combined with a character generator in a vision mixer and rerecorded (written) on the same place on the tape.
To get the maximum advantage from a digital VTR it would have to be used in an entirely digital environment, i.e. digital camera, digital vision mixer in the edit suite and so on, but there is still a spectacular improvement when digital VTRs are used in an otherwise analogue environment.
A further complication arises as it is possible to work component or composite in either analogue or digital.
A composite signal utilises one wire to carry all the picture information. A component signal, such as Betacam SP, uses three wires, one for the black and white information and two for the colour information.
While the component is a better way to process television signals, giving better quality pictures, it is not a convenient way to distribute those pictures to the viewer. All national analogue terrestrial transmissions are composite systems – PAL in the UK and most of Europe, SECAM in France and Russia, and NTSC in America and Japan.