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Monday, October 11, 2010

A little bit of information about the different cable connectors

What is SCART ?

SCART is a connector that was designed by the French. In a short moment of brilliance, the government in France made it mandatory for every TV set sold there to have the SCART connector. This sort of forced all big TV makers to include a SCART connector on every TV that was shipped to Europe (or built there).

SCART is NOT (I REPEAT: NOT) a definition of signals.

Instead it bundles a range of analog signals that are (were) commonly used in relation to TV's in ONE standardized connector.

SCART usually incorporates the following video signals:
1) Composite video
2) S-video
3) RGB video

I say usually because not all devices support all signals. F.I., a VHS videorecorder, by nature, does not support RGB signals. That is because the video is recorded on the tape with a signal that is simular to composite video.

Every TV however, should have at least one SCART connector that allows input of any of these signals.

(SCART also supports audio signals of course, but I leave them out of this thread, because they will be rarely used in our hobby, most people connect speakers to the PC running Mame, or in original cabs, the installed audio amplifier and speakers are used).


What is RGB video ?

RGB video is the most basic form of video signal you can have in relation to CRT driven color TV's. There are separate wires for each basic color Red Green and Blue, and one for the sync signal. Because of this, none of the signals can influence each-other. In good quality SCART cables, every signal line has it's own shield (return or ground)to further prevent cross-talk between them and other wires.

Every color TV in the world is decoding whatever signal (HF through Antenna, composite video etc.) is input to it into this basic RGB signal, before it feeds it to the CRT. So, if we use the RGB signal on the SCART connector ALL the decoding electronics in the TV are by-passed, ensuring the best possible picture quality. By doing this we use the TV exactly like a "real" arcade/open frame monitor.
There is NO quality difference in picture between a "real" arcade monitor or a TV that is used with RGB.

How about the other signals ?
Well, first there was Composite video. The one (and only) advantage of this signal is that you can transport it through a single wire (and a shield). To make this work, all the color info AND sync info is combined into one signal. The TV will have to decode this signal into all the seperate colors and sync again. This process causes a significant loss in picture quality. Composite video is NOT recommended to be used for our hobby because of this.

Then there's S-video. With S-video you have one wire for the sync, and one wire for ALL the colors. So the colors are still combined. This still requires decoding in the TV, and still introduces a reduction in quality. Outside of Europe, this is often used in our hobby, because only European TV's have SCART.
I would not recommend it, because RGB is the best option to choose, and it's present out the outputs of your PC or original game PCB.

12 comments:

  1. Thanks for the information! and yeah, every tv should have SCART!

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  2. nice post thanx the post u help me thnx very much

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  3. I like your post and I would really like to see more of them

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  4. yeah man, scat all the way! :D

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  5. yep..is the great post thnx for the info

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  6. scart..
    very useful information

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  7. Thanks your blog is great for computer users.

    ReplyDelete