Does anyone know a site which gives an explanation of what the different connections are and explains why one is better than another. RCA plugs and S-Video I understand but Component, Composite, RGB etc. are the ones I would like more information about.

betje

This may not be detailed enough for you, but it's a start.
http://www.dba.org.au/index.asp?sectionID=95

BTW, I think you'll find that composite is the same as what you are calling RCA plugs.

I'll have a go at a simple explanation.

Video originates as an RGB signal, i.e. 3 colour signals mixed in differing intensities to create a range of colours and shades. It is possible to carry these signals separately, or to separate the colour information from the luminance information and then carry the resulting signals in different ways.

One way to carry these signals is to combine them. However, once you combine the separate elements of a video signal you cannot separate them perfectly again, so you degrade them to varying degrees.

In order of quality, these are the options.

DVI carries RGB as a digital signal. It's potentially the best quality.

RGB (in it's various forms) carries RGB as separate analogue signals. RGB usually requires separate timing or (sync) information, either as 2 signals (one horizontal one vertical, i.e. RGBHV or VGA) or one signal (usually a composite video signal that provides the timing information, i.e. Scart RGB). Sometimes the timing is part of the green channel, this is called RGB "sync on green".

Component video separates the luminance information from the colour information and produces three signals - the luminance (Y, a black and white video picture) and the colour difference that represents the blue (Pb) and red (Pr) information. This process results in very little loss of information and so, if decoded well, it is very close to RGB in quality. This system can also carry higher frequency information, so is also suitable for HD.

S'Video carries luminance on one wire and the colour information (Pb, Pr) combined on another wire. S'video cannot carry the full potential resolution of standard definition and so is not suitable for HD.

A single RCA plug carries composite video, i.e. the colour and luminance signal are carried by one wire. Composite is convenient, but it was designed to carry TV signals of relatively low quality.

The other issue here is because video signals contain high frequency information (higher frequency = higher definition) it's important that the cables you use are suitable. Ideally cables are 75 Ohm impedance, as are their terminations (i.e plugs and sockets). The higher the frequencies you are dealing with the more important this is.

The 3 x audio cables usually supplied as component video cables (with a lot of equipment) are often the cause of poor HD PQ. Audio cables and connectors are designed for much lower frequency signals, and have the wrong impedance characteristic for video.

You could also have a look at this link
http://www.avforums.com/forums/showthread.php?t=43445
which is quite good.

Steve B.

for a discussion of component video:
http://members.aol.com/ajaynejr/compon.htm

This isn't really related, but I'm a bit annoyed at how many SD STB's do RGB via scart, but not component video. Since it uses the same pins and can be implemented in the software without any extra hardware needed, I don't see any reason to exclude component, especially considering so many TV's now use it. Some examples are the Nordmende, Samsung and Thomson.

Or it should be the TV's that should support RGB, the picture tube shoots out RGB!

Send me a PM if you need to ask anything about cables and connections - always happy to answer questions

Thanks to everyone for your help. Much appreciated.
betje.