Digital Video Technology
Digital technology offers significant advances in quality, delivers effects not possible with traditional analogue equipment and speeds up the achievement of a polished product. It has revolutionised graphics and although costs are high for small installations, it is becoming more attractive with the falling price of computer memory. It is now possible to build an almost entirely digital station that is not prohibitively more expensive than a traditional installation, however, top-end devices remain expensive and the cost- conscious user needs to consider carefully the level at which to invest. Hiring a facility, if it is only occasionally needed, may be a cost-effective alternative.
Whilst some advantages of digital technology may be marginal for the small facility, it seems likely that the availability of traditional analogue equipment will reduce in the future but not in the short term. The decision, therefore, is not an easy one. The major advances afforded by digital technology are most sharply focused on video effects, graphics and post-production.
Digital graphics are discussed on page 88. Digital post-production is a more recent development which has been made possible by the enormous increase in computer memory now available. This enables random access of recorded material and thus speeds up the editing process considerably. For a more comprehensive discussion see pages 164 and 166.
Digital video effects
There are many types of digital video effects (DVE). Basic devices can manipulate one picture in two dimensions and offer a freeze frame capability. Sophisticated machines permit the manipulation of two or more pictures simultaneously, can introduce perspective into a two-dimensional image and apply distortions that bend, zoom, rotate on any axis, do page turns etc., as well as memorise sequences. In general, the more sophisticated the device the more it costs.
Picture stores
Often installed in the graphics area, picture stores are able to record stills or ‘grab’ moving pictures and automatically index them. Browsing through the stores by displaying a ‘polyphoto’ is possible and picture selection is fast. Some advanced equipments offer the full archiving facilities of a picture library.
Standards conversion
The British television standard uses 625 lines to each picture, with a picture repetition rate of 25 per second. The American standard has 525 lines and 30 pictures per second. Three main colour systems are in use: NTSC (mainly USA and Japan), SECAM (Francophone countries and a modified version in Eastern Europe) and PAL (most other parts of the world including UK). Programmes cannot be interchanged without conversion. Standards converters are usually hired when required, although domestic quality VHS recorders are now available for viewing quality conversions. Some videotape machines and monitors have a multi-standard playback facility.
Although the above devices may be independently fed to the studio they may also work in combinations or off-line to generate programme material prior to a studio session or afterwards to ‘doctor’ pre-recorded material.
1. Pallette and stylus for computer graphics machine.
2. Electronics associated with the various devices.
3. Digital video effects (DVE) control panel.
4. Vision mixer/downstream keyer.
5. Edit control panel for videotape machines.
6. Character generator.
7. Videotape machines.
8. Preview monitors.
9. Output/transmission monitor.
10. Loudspeaker (another may be required for studio talkback if on-line use is anticipated).
Other devices such as slide-file and colour correctors may also be made available to the work station.