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ALTHOUGH THE Videokalos Colour Synthesiser may not offer a specifically
new technology - like the digital effects processors eagerly awaited
by PAL broadcasters - it's novel conception seems to offer intriguing
flexibility for synthesising and manipulating colour images, and for
other kinds of effect.
The synthesiser can manipulate five inputs independently - colorizing
monochrome sources or varying the level and gain of the colour components
(RGB) of colour sources. Together with the synthesiser's other features
- three further inputs to a wipe generator and keying panel, and a four-bank
(ABCD) eight-input switcher - the whole unit can be used either as the
main mixer in a small studio, as a sophisticated postproduction mixer
in editing, or as a special effects unit for broadcast studios. (The
device has its own built-in sync pulse generator, switchable to PAL
or NTSC, but can equally well be locked to a broadcast studio's generator.)
The synthesiser represents an essential rethinking of the design and
layout of control equipment, incorporates a range of functions normally
handled by separate pieces of equipment, and it brings before one operator
a range of controls that would in most existing broadcasting studios
be spread out between different operators and locations. Some effects
are usually at the disposal of the vision mixer - and sometimes the
electronic effects operator - but any such complex variations of colour
balance are normally handled separately in the vision control room,
physically separate from director and vision mixer, before the source
is presented to the vision mixer.
The synthesiser is claimed to be "the first true video 'mixer'
in the sense that we have come to use the term when referring to audio
mixers". According to the synthesiser's designers, most existing
TV mixer units "do not allow one to control and modify the parameters
of the electrical signals of the selected sources has become common
practice with audio." The synthesiser's affinity with a musical
instrument or electronic music synthesiser are not surprising, given
the equipment's origins.
It was designed by Peter Donebauer and Richard Monkhouse - Donebauer
works as a visiting lecturer in Experimental Video at the London College
of Printing, where one of the first synthesisers is installed. He is
an established video performance artist and needed a device that gave
him precise control in manipulating images, but in an extremely portable
form - the synthesiser is a self-contained panel 6" x 22"
x 41" and can be supplied with a flight-case. Monkhouse has designed
a number of audio synthesisers.
The synthesiser's eight channels are mixed in the switcher section at
the right of the panel. Most mixing is done on the AB banks. The twin
outputs of the CD banks can be used for preview, special effects processing
external to the machine or for re-entry to the AB banks - although the
facilities elsewhere on the panel should make this option normally superfluous.
A single picture source can be fed to two or more of the five colouriser
inputs simultaneously, so several different manipulations of the image
- colourising a monochrome source or rebalancing RGB on a colour source
- can be accomplished simultaneously and independently. The operator
can then cut or mix between them on the switcher.
The synthesiser's other three channels (6-8), each with its own independent
key, provide an extremely versatile range of special effects, together
with a wipe generator permitting horizontal, vertical and corner wipes
and a variable wipe consisting of two ellipses. (The interference area
between the two variable ellipses gives the wipe waveform such as circle,
cross or "flying saucer".)
A 22 x 22 hole patchboard is used in conjunction with the three keys.
Each key may select as its triggering source any of the five monochrome
inputs to the colouriser, any of the 15 RGB colouriser outputs, the
other key channel outputs, the wipe generator or an independent external
key output. It may also select any combination of RGB outputs of the
colourising section, which, by varying the balance of the three colours
at this point allows full chroma-key off any colour of an original scene.
Three independent chroma-keys are thus possible. The operator may also
key off a combination of channels, equivalent to keying off a mix of
two to seven channels simultaneously.
Any combination of colours, from any source in the synthesiser (including
the other key inputs) may be placed on each side of the key. By using
the patchboard the three key channels may be ganged sequentially and
set for different key levels. This provides up to four levels of colourisation
of a single image, with full analogue video information within each
level rather than the block colour effect usually seen in quantising
effects. Moreover, as positive/negative colour mixtures are possible
within each level a very complex colouring potential can be achieved.
It is difficult to gauge what response the equipment will find from
TV engineers who normally purchase and install studio facilities, nor
its impact upon traditional job demarcations. But clearly the versatility
of effects that are possible - and possible under more creative control
than previously available - should excite television producers, particularly
those interested in exploiting the potential of the studio, and those
working on music programmes. And, indeed, several producers have already
trekked to the Brixton cottage industry, and are interested in hiring
the synthesiser for specific programmes.
Technical notes: The AB banks produce an encoded signal switchable to
PAL or NTSC - alternatively RGB can be fed to an external encoder for
SECAM - and one of the first synthesisers was shipped to Paris. The
synthesiser also incorporates a colour bar generator and provides outputs
of oscilloscope drive waveforms.
The Videokalos Colour Synthesiser - on the left the five colouriser
inputs with separate controls for RGB level and gain on each input;
in the middle three further inputs with keying and wipe controls; and
on the right the 8-input ABCD mixer panel.
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