What is Composite Video?

A composite video signal is where all the colours and luminance information along with the necessary timing signals are all squeezed (or encoded) into one combined signal. Inevitably there is some loss and compromise involved with this process. This manifests itself as a lack of detail in the picture and a general blurring compared with the original RGB signals. In the UK the system of encoding used is PAL with NTSC used in the states. It is PAL encoding that is responsible for the moiré patterning sometimes seen on newsreaders suits or check shirts etc. Composite video is the yellow single phono connection on your VCR or TV and is the usual method used in a scart connection. Composite video uses a 75R cable for connection. A composite signal is decoded in your TV set to recover the original RGB signals and timing information. Typical bandwidth of a composite video signal is only a couple of MHz. In the UK the Luminance or brightness information is derived from the RGB signal and then the colour is added to this at a frequency of 4.43MHz. This inevitably limits the available bandwidth to considerably less than 4.43MHz. A similar system is used in the USA but the colour here is at 3.58MHz. See the section on converting NTSC to PAL for more detail but it is the different colour frequencies that gives rise to the problem of black and white picture when an NTSC video is played on some compatible VCR's