Technical information

© CLEAPSS 2005 1621 ICT in the Science Department
16.6.4 Video connections and adaptors
The output of a camera needs to be fed into the input of the display or storage device
(computer, TV monitor, data projector etc). Usually the inputs and outputs on equip-
ment will be via sockets and the leads that connect the pieces of equipment use a
variety of plugs. For details of computer connections, see section 16.5.5.
For recently-purchased equipment, suitable connector leads will have been included.
Existing and older items may, however, have obsolete connectors so that the leads
supplied cannot be used to connect together old and new devices. Information provided
in this section may help in obtaining suitable connectors and adaptors.
Analogue signals
These include the following.
• Composite video [brightness (luminance) and colour (chrominance) comb-
ined with synchronisation signals].
• S-video [separate luminance and chrominance signals].
• RGB [separate red, green and blue signals each with synchronisation].
• RCA [composite video on one lead with one or two leads for audio signals].
• Modulated UHF [transmission quality is relatively poor because the signal
is modulated onto a UHF radio wave and demodulated at the other end].
For the transmission of each of these signals, leads with various connectors are
used. In addition, SCART connectors, consisting of 21 pins that can be configured
in different ways, are sometimes used.
Digital signals
The most common system for digital video signals is USB. USB 2 is faster and
compatible with the earlier USB 1, though there may be software problems.
Firewire, which some equipment uses, provides a faster communication channel.
Adaptors
While it is possible to find adaptors that will enable devices with different conn-
ectors to be coupled up, converting the signal between analogue and digital
formats can degrade the quality of the image. There is also no guarantee that the
adaptor will work at all unless the equipment to be connected is known to be
compatible. Table 16.6 discusses some commonly-available adaptors. Illustrations
of a variety of connectors used in such adaptors are provided in Table 16.7.
Table 16.6 Adaptors available for video connectors
To:
Devices with different types of analogue
input including: composite video,
S-video, UHF and RGB.
Connectors include: Coaxial, UHF, BNC,
Phono, SCART.
To:
Devices with different types of digital
input:
USB 1, USB 2, Firewire.
From:
Devices with different types
of analogue output including:
composite video, S-video,
UHF and RGB.
Connectors include: Coaxial,
UHF, BNC, Phono, SCART.
Adaptors are generally available.
Sometimes, two adaptors need to be
'daisy chained'. For S-video to SCART
connections, images may appear to be
black and white because not all SCART
sockets / leads/ adaptors are S-video-
enabled. There may be an S-video setting
on the receiving device. Adaptors for
RGB devices are expensive.
A video capture card, or an external USB
adaptor / capture device, with the appro-
priate input socket is needed. These can
be quite expensive (£50-£150 at 2005
prices).
From:
Devices with different types
of digital output:
USB 1, USB 2, Firewire
Images from a camera with a digital
output can only be displayed via a
computer and graphics card with a
suitable output.
Adaptors are available for some connec-
tions. Sockets (ports) and plugs for USB 1
and USB 2 are physically identical,
though USB 1 devices plugged into
USB 2 ports only work at the USB 1 rate
and USB 2 devices might not work in
devices which only have USB 1
capability. Sockets of the appropriate type
may be added via an expansion card.