Composite Sync versus Composite Video

Started by kwyjibo, April 03, 2007, 10:23:27 AM

Previous topic - Next topic


When I was doing a RGB video cable por my Megadrive (Genesis) I noticed one thing: using the composite video or the composite sync output of the megadrive to feed my TV throw different results.

With the composite sync, the picture was noisy, so I used composite video.

With that info in mind, I remebered the problem I had with a french NES. The french NES has RGB output, so I bought one to have a picture improvment. But when I tested I discovered that the picture was poor, worse than composite video. It was noisy, in the same way as it was the megadrive with composite sync.

I tested to connect the french NES to a SCART socket without RGB support, to see if the NES was using a composite video for syncing. This test produced no picture.

So, what we have:

- My TV doesn't like composite sync
- French NES uses composite sync

Does anyone now a workaround to make my TV accept composite sync for RGB signal, without a noisy result?


Try a different TV first. Then, maybe try feeding the composite video signal through a sync seperator such as the LM1881n:
That will give you a clean sync output.


Does the fact that France used SECAM, and ONLY SECAM for the longest time have anything to do with the method of sync in question?
I would imagine a French NES is SECAM.


Were you connecting the French NES to a LCD or a CRT TV?
I did some checking, and noticed the picture quality between a French RGB NES and a composite PAL NES on my CRT was quite different. Colors on the composite seemed a bit washed out and there was noise in the image. So in that regard I would say the French NES' RGB looks better. Some photos:


Please note: you're replying to a seven year old thread.


haha, me too!

I'm interested in what's in this french nes, I've had a peek inside a french atari 7800 before and all it was doing was taking the atari's native luma and chroma (svideo more or less) signals and converting them to rgb via a daughter board. the result was a noisy picture with dot crawl, less than impressive colours and poor definition.
the problem is that in france there were only the two choices secam and rgb. I'm not aware of any consoles which output secam, they all seem to have gone with the rgb option (less complicated maybe?).
However, just because the console is outputting rgb does not mean it's outputting quality rgb, they simply wanted a workable picture as cheaply as possible, crudely converting inferior video to rgb gets the job done, most countries were happily using RF at the time so that was the par quality, regardless of the delivery method.

anyone got photos on the inside of a french nes? or even better, one for sale?


Same thing, just a low-quality composite->RGB convertor board. 


Quote from: Lawrence on June 02, 2014, 09:07:03 PM
Same thing, just a low-quality composite->RGB convertor board.
IIRC it's based around a Sony V7021 decoder chip. The French Atari 7800 uses the same decoder chip as well, but I don't know if it takes in composite video like the NES or chroma/luma.