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Composite v Component

Ian Vinten

Standard Member
We're about to get a Plasma here at work (thanks all at AV-Sales :smashin: ) and we're getting our usual guy to come and fit it.

Now, I want to get it hooked up with component as we have a progressive DVD player and a beta machine on the way but our guy thinks that composite is the way to go as apparently we 'won't notice much difference if he uses good quality leads'.

I thought composite wouldn't even get close to component no matter how good the connectors are... Has anyone ever seen a composite connection that's any good?
 

Ian J

Banned
Ask him to bring both so that he can demonstrate the superiority of composite to you. :thumbsdow

Assuming that you have Sky at home, try switching the output of the Sky Box between composite and RGB to see the difference - use the little score box in the corner of a football or cricket match as a test.
 

Ian J

Banned
No, all composite can manage is a crap signal. the reason that i suggetsed the RGB test is because RGB is the Uk equivalent of component and of broadly similar quality.
 

GalacticaActual

Well-known Member
There is no way that composite will give you a better picture than component. You will get dot crawl, cross colour interfernce, and a softer picture using composite, especially on a plasma. Componenet will give alround better results, with RGB and then Svideo all being better than standard compsite.



In the days before DVD, this topic wasn't relevant to the vast majority of home theatre enthusiasts. Most of us would have used the RF (antenna) output of our VCR to connect up to our TV. Some would have gone a little further and connected up using the composite output because it looked better. A small, very fortunate minority of us, had to grapple with the intricacies of hooking projectors up to video sources.
Things have changed. DVD has brought a new level of readily-accessible video quality into the home environment, and along with it, several unfamiliar ways of connecting up to your video display device to access this additional quality.

Before we can discuss the nitty-gritty of the various video connectors that you will find on the back of your DVD player, we need to briefly discuss just what is recorded on a DVD and a little about how it got there in the first place.

What comes out of a TV camera?
A TV camera outputs a video signal that is split into the three primary colours; red, green and blue (RGB). The entire colour spectrum can be represented by varying intensities of these three colours. This signal needs to be modified before it can be further processed or broadcast. Why?
Problems with the RGB signal
The RGB signal has two specific problems associated with it in the professional video world. Firstly, it has a very high bandwidth. Secondly, the colour and the black and white picture information are combined within the RGB signal. This is dealt with in the professional video world by converting the RGB signal into a component signal, also referred to as a YPbPr or YCbCr signal. The Y component of this signal is the black and white information contained within the original RGB signal. The Pb and Pr signals are colour difference signals, which are mathematically derived from the original RGB signal. For our purposes, it is sufficient to understand that the Y signal contains full bandwidth black and white picture information, and the colour difference signals contain bandwidth reduced colour information.
It is important to realize that component video output and RGB video output are not the same and are not directly compatible with each other, however, they are easily converted either way using a transcoder. Note that transcoders are generally professional-level video equipment and priced accordingly. You should expect to pay around $1000 US for an external transcoder, so this is an impractical solution for all but those of you with high end projection equipment and/or a high end DVD player. Here is an example of the sort of equipment that you are looking at.

What's recorded on a DVD?
DVD stores a component video signal in digital format. Since this is the native video format that is stored on DVD, this is also the best format to use to display the picture, if your equipment is capable of dealing with this type of signal. In Australia, virtually no equipment exists that is compatible with a component signal, though there is some that is compatible with an RGB signal. Many DVD players are capable of converting their native component signal to an RGB signal, but this varies on a player-by-player basis.
Problems with the Component signal
As discussed above, DVD stores its video information in the component form, but unfortunately the great majority of us cannot take advantage of this format. The designers of the DVD format anticipated this, and made allowances for it in the specification. All DVD players are capable of downconverting a component video signal into a more suitable format for display on the current generation of consumer display devices. The first such downconversion step is to S-Video, which is a connector that will always be found on any DVD player.
S-Video
Remember that the component video signal is split into three parts; black and white information (Y), and two colour difference signals (Pb and Pr). The S-Video connection keeps the all-important black and white (Y) information separate, and combines the colour difference signals into a single colour signal (C). Instead of three separate signals going to the display device, there are now two separate signals.
As you would expect, combining the two colour signals results in a degradation of the colour information. In the grand scheme of things, this is a fairly minor degradation, and you still get an exceptionally good picture from this signal.



Composite
What about if your display device doesn't have an RGB, component or S-Video input? Well, then we downconvert another notch to composite video. As its name suggests, composite video is a single video signal that is a composite of the black-and-white information (Y) and the colour information (C). This is the same type of signal that at least some of us will have been using prior to the advent of DVD to connect up our laserdisc players or VCRs.
Composite video signals have a number of unavoidable image problems because of inherent limitations of the PAL and NTSC systems. The problem is, once the colour (C) and the black and white (Y) information have been put together, they can no longer be perfectly separated due to fundamental design limitations of the two systems. Whilst a detailed description of these image problems is beyond the scope of this article, there are two specific artefacts which I will mention which are readily demonstrable.

Dot crawl. This occurs on the boundaries between two colours where you can see moving blocks of incorrect colour information. The simplest way of demonstrating this artefact is to look at a test pattern on your TV. If you have access to either Video Essentials or A Video Standard on DVD or Laserdisc, take a look at a colour bar pattern. On the Video Essentials DVD, this is located at Title 10, Chapter 10, amongst other places. In particular, look at the vertical edges between the colour bars. You will notice that the edges are smeared, with little blocks of moving colours throughout in a regular pattern. If you then compare this same test pattern via an S-Video input, you will see that these blocks have disappeared, and the edges of the colours are sharp and clear. What applies to a test pattern also applies to normal images that are displayed with composite video. They, too, will exhibit dot crawl at the boundaries of different colours on the screen.

Cross-colouration. You may be familiar with this artefact when watching a black-and-white image on your TV, particularly if it is an older model. Fine lines in the image result in a purple colour being displayed by the TV. If you look at the test pattern shown on the right (Title 17, Chapter 23, Video Essentials) via a composite video output, you will readily see if your TV is prone to this artefact. If you look at the same test pattern via an S-Video input, you will not see this artefact.

Conclusion
In a nutshell, if your display device can support it, a component or RGB video connection will give you the best possible image from DVD. An S-Video connection is not far behind in quality. A composite connection, however, will result in a perfectly acceptable, but less than optimal result from your DVD player.
 

Gordon @ Convergent AV

Distinguished Member
AVForums Sponsor
Play the opening sequence of Star Trek Insurrection. The hay the kid jumps out of will be covered in crawling artefacts with composite along with splatters of ranbow colours)...then in the top left corner, after the pan over the bridge you'll see what appears to be one of those wooden bars that horses get tied to in westerns. It'll basically be a rainbow colour......

Then play it back from component and look in wonder as you now see hay that looks like hay (presuming your plasma does film detection, if it doesn't you'll get some jaggies but NOTHING like as bad as with composite).

If you really want to mess with his head get DVE and look at Title12 Chapter8. If you can;t see difference with that test pattern then he needs to see a psychiatrist, not an optician,

Gordon
 

LFCRules

Novice Member
Digital Video Essentials. It's a calibration DVD disk you can get to help setting up the picture on your plasma to get the best from it. You can get them from variosu places, including AxelMusic. Check them out here

There are various threads about them in the plasma/projector forums.

Thanks

Andy
 

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