Video Signals Types Explained
Composite Video
The most common used way of transferring CCTV images to a monitor from another piece of equipment is by using a single coaxial cable with a BNC at each end.
The video signal sent along this cable is known as Composite video.
It has also been used for many years by consumers with VCR’s, camcorders etc…
A composite video signal is passed between one piece of equipment to the other over one single coaxial cable. At each end of the coax within a CCTV system is a bayonet type connector, called a BNC connector.
On some plug and play systems at the cheaper end of the market these are sometimes replaced with phono plugs usually coloured Yellow.
As the word Composite would suggest, all of the components needed to produce the video image are transmitted together in one composite signal. The Colour (chrominance), B&W (luminance) and video sync pulse are all sent along the one cable.
This makes Composite video a very convenient way of transmitting video signals from one place to another as only one cable is required.
The only downside of this is that the different parts of the signal can sometime interfere with the over picture quality, but for most applications the images produced are more than acceptable.
S-Video
o combat any degradation of the video image that can sometimes occur with Composite video, the makers of high end CCTV video equipment developed a different way of transmitting video signals.
The component parts of the video signal, Colour (chrominance), B&W (luminance) and video sync pulse are kept separated to reduce any chance of interference, this was called S-video.
The signals are transmitted along twin coaxial cables with a miniature 4 pin DIN plug at each end.
They are usually marked and defined by “Y” for luminance and sync pulse and “C” for chrominance.
Most CCTV equipment with S-video sockets will also have Composite sockets too so the end user can choose what suits them best, although S-video is regarded as the better quality.
Component Video
hen movies became available on DVD everyone was amazed by the high quality of the images produced.
The very name DVD 9Digital Versatile disc) suggests that the information on the disc is held there in a digital format, which enable the sound and video content to be recorded and stored in very high quality.
The images are split into component video, which basically means the video signal is split into even more component parts than S-video. The signal now has Luminance and sync pulse “Y”, with the chrominance “C” being separated into “B-Y” (Blue less luminance, also know as Cb or Pb) and “R-Y” (Red less luminance also known as Cr or Pr)
These are usually made up of three coaxial cables with BNC or phono plugs at each end.
RGB Video
nother type of component video is found typically on consumer video devices such as DVD’s and TV’s.
These are called SCART connectors, these use multi-core cables with a SCART plug at each end, consisting of 21 pins, these are also known as euro-connectors.
This method of video transmission separate the three main video colour components “R” Red, “G” Green and “B” Blue, hence the name RGB. Depending on the grade of cable and how many of the 21 pins are used the sync pulse is sometime separated from the Green video providing a better quality video signal.
Please note! that just because a SCART socket is used, this does not automatically mean it is RGB.
Composite, S-video or RGB can all use SCART connectors, however they can only be used one at a time and cannot be interchanged. Some high end equipment allows for the option to be chosen, if not refer to the user manual to confirm the signal format available.
PAL and NTSC
PAL video was adopted by Europe, Australia and New Zealand where as NTSC was adopted by the USA and Japan.
Almost all the video formats discussed above will work on both PAL and NTSC with the exception of RGB component video which is mainly found in Europe using the PAL system.
When purchasing consumer video equipment, bear in mind that PAL and NTSC are not compatible.
However, most Monitors and TV’s now have the ability for the end user to choose PAL of NTSC when setting the kit up.
