Tips T0011

Video Connectors
Connecting a number of pieces of video equipment together can sometimes be a cause of misery, so we've put together an explanation of the more common video connection types and explain the relative advantages and disadvantages of each type.

UHF
UHF (Ultra High Frequency) is the method used to transmit standard television pictures using an aerial. Some older camcorders have UHF outputs which allow you connect the camcorder directly into the back of a television. UHF signals work by combining (modulating, in the technical terminology) both the audio and video signal onto a carrier signal. You can use your TV to tune into this carrier signal, from which the TV can then extract (demodulate) the video and audio information.

Although UHF is compatible with all TVs, this modulation and demodulation process causes the video quality to deteriorate. Picture quality is poor and only mono audio is supported from the camcorder.

If you wish to play back video from a non-UHF source to a UHF TV, you will need to buy a box of tricks called a modulator. This contains the electronics needed to add the video and audio signals to a carrier signal, suitable for UHF.

Composite Video
Composite video is possibly the most popular form of connecting video equipment at the consumer level. Composite video does not contain any audio data and the video signal is sent usually sent down a 2 wire phono lead. Where several phono connectors are bunched together (see picture), the composite video connection is coloured yellow.

Composite video is a much higher quality than UHF, as the signal does not have to modulated and then demodulated onto a carrier signal. The problem is that not all TVs have composite video inputs. You may however buy a composite video to SCART adapter which will allow you to view the video on any TV that has a SCART socket.

When choosing a composite video lead, try to avoid the really cheap, thin wire leads that can come free with equipment. Also, avoid using normal audio phono leads for composite video. Thin wire leads can lead (sorry!) to degradation of the picture quality, especially over long distances. Additionally, thin leads are more susceptible to interference than proper video leads.

S-Video
Potentially improving video quality still further is S-Video. S-Video is a video-only connection (i.e. there isn't any audio signal), but rather than send the video signal down 2 wires like composite video, S-Video sends the color and brightness information separately down a total of 4 wires.

We say that S-Video can potentially improve quality, because it depends on what format the video originated. If the video equipment uses separate color and brightness information internally and sends these signals down the S-Video connection, the maximum quality picture will result. If however the equipment simply separates an existing composite video signal into its color and brightness values, the S-Video signal will be no better than the original composite signal.

SCART
SCART is a 20 pin connector that is used to connect television and video equipment. SCART connectors carry both audio and video information, and in fact they can carry several different formats of video.

This ability for SCART to carry several different formats of video is usually the cause of many SCART problems. Suppose we have a SCART output from a computer which sends separate red, green and blue signals for maximum quality. We can then plug the other end of the SCART lead into a TV which only recognises the composite video signal on the connector. We now have a situation where two items of equipment which both use SCART cannot connect to each other.

In practice, a lot of SCART equipment just uses the connection to pass composite video along with a stereo audio signal.

FireWire
FireWire (also known as i-Link or IEEE1394) is an all digital form of connection, sending both video and audio data down a 4 or 6 wire connector. Strictly speaking, FireWire is simply the connection type and data protocol and DV is the actual video format that is sent down the cable. However, the both FireWire and DV are usually referred to as the same thing.

FireWire allows the sending of more than just video data, although video is currently the most popular use for the standard. The resolution for DV video is fixed depending on whether you are using PAL (720 x 576) or NTSC (720 x 480) and is significantly better than any of the above analogue video formats.

FireWire is currently only really used to do camcorder to camcorder copies or camcorder to PC video editing.

Summary
The following table summarises the different video connection formats:

*Digital connections allow multiple copies of video and audio material without loss of quality. With an analogue connection, quality is lost every time a copy is made