Mega Drive video output - Technical Q

[JDB]

I hook all my Mega Drives up to my CRTs with RGB SCART connectors. When I hook up my Mega Drive 2 the picture is absolutely flawless, every pixel is square and sharp, the colours are vibrant and life is good.

When I hook up my MD 1 up it looks just the same, except that there seems to be very faint regular vertical lines (where the colour is very slightly off) a few pixels wide spanning the screen.

I've tried different TVs and the problem is more apparent on larger screens (well that makes sense, cos each pixel is bigger on a larger screen). I've tried several of my Mega Drive 1s, early ones without the TMSS are affected just the same. When I connect my 32x to the MD1 the problem vanishes (also makes sense because the final picture processing is done by the 32x).

The thing is, has anyone experienced this? Does anyone know the reason for this. I'm guessing opamp chips/RGB encoders that are wearing out or just aren't up to the task or some periodic noise affecting the scanlines (because the lines are vertical and regular).

[lordofduct]

Haven't experienced it... but it has to do with the sync of the RGB signal.

The Genny1 does use a different composite signal encoder then the Genny 2... maybe the problem is in that.

Or maybe it's just a bad resistor on the end of the signal pin going out of the Genny1...

[evildragon]

Composite video and composite sync are two different things...

I have vertical bands on component video transcoders, but only VERRRRY faint. Genesis 1 non-tmss..

[Joe Redifer]

When I connect my 32x to the MD1 the problem vanishes (also makes sense because the final picture processing is done by the 32x).
Are you sure you are running in RGB mode? It sure doesn't sound like it. The 32X can't clean up the RGB from the Mega Drive, but it can clean up the composite. What you describe sounds exactly like the problem with composite video on the system. I am running RGB from my Genesis 1 and there are no vertical lines like that either with or without the 32X attached. In fact the video looks sharper without the 32X attached since the 32X does introduce a generational loss in the video when running everything in RGB.

[matteus]

I brought a megadrive 2 off ebay sometime ago and it came with a Audio/Video (Composite) cable only made up of 1 video (Yellow) and 1 sound (White) I'm guessing this createa 1 channel mono?!? Is this normal or should there be a Yellow Red & White cable of this type?

Additionally I've seen a scart cable

http://home.clara.net/robwebb/shop/megadrive/megadrive.htm

Will the scart on this page be an improvement over the Composite cable?

[playgen]

A full RGB scart cable will give a clearer image over composite, each pixel stands out, without the blurring that composite gives.

[matteus]

so its worth the 10 quid price tag? hehe is there anywhere i can get some new 6 button pads from ?

[playgen]

£10 seems to be the standard price for them. Wether you want the extra clarity is down to personal choice. I prefer using composite myself as RGB makes everything look more blocky, especially on a big TV, but most people seem to prefer that.

[matteus]

an almost anti-aliasing effect then.....it would make sense for it to blur seeing as the technology at the time wasn't meant to have a crisp finish to every pixel

[playgen]

Yep thats exactly how I see it, as anti-aliasing. I recently got a RGB scart lead for my gamecube to replace the standard composite lead, and although the colours appear a bit brighter, there far more jagged lines. What I had presumed the console was smoothing out with its hardware anti-aliasing, was just a side-effect of using composite.

[Kogen]

Well it is that, as developers knew it would blur and specifically added "fake" effects. Really they should all look bad on large TVs as they weren't intended to be on them.

I think using RGB with Ecco, for example, makes the water look terrible without the blur.

[Joe Redifer]

I'd take this:

http://www.joeredifer.com/crap/cast1.jpg

http://www.joeredifer.com/crap/bman2.jpg

over this:

http://www.joeredifer.com/crap/cast2.jpg

http://www.joeredifer.com/crap/bman1.jpg

ANY DAY.

[David J.]

I'd take this:

http://www.joeredifer.com/crap/cast1.jpg

http://www.joeredifer.com/crap/bman2.jpg

over this:

http://www.joeredifer.com/crap/cast2.jpg

http://www.joeredifer.com/crap/bman1.jpg

ANY DAY.

Hooah!

It was so worth the $$$ (it's a bit more expensive in the USA)

[Sublevel]

Hello!

Im thinking about importing a Genesis 2, and i need to know a couple of things.
Which Genesis models supports RGB? I know the Genesis 3 Core does not, so i wonder if the Genesis 2 Core model supports RGB? The one that came only with console and controllers. Are there any differances between a regular Genesis 2 and a Genesis 2 Core model?

Thanks a lot.

/Sweden

[TmEE]

ALL of them (MD1 and MD2, don't know about 3) support RGB.

And I got these vertical lines form my MD2 too, using RGB... I got rid of the lines by building my own composite sync out of H and V sync that MD VDP outputs (and fixed the screen shifted to left issue in the process...).

[Sublevel]

ALL of them (MD1 and MD2, don't know about 3) support RGB.

And I got these vertical lines form my MD2 too, using RGB... I got rid of the lines by building my own composite sync out of H and V sync that MD VDP outputs (and fixed the screen shifted to left issue in the process...).

Does every Genesis suffer from this? I know nothing of soldering or building my own cables..

[TmEE]

I have no idea, all mine do... and there's no cable soldering, but 5 tiny parts and few wires

[Mr. Ksoft]

Speaking of video output and building on what's been said already:

On my Gen. 2, I've got these faint vertical lines that have been mentioned, along with a kind of solid border color on the left side of the screen only that "melts" into the image... is this normal or is it caused by the (maybe very cheapo) yellow-white-only composite video cable I've got? Also, you can see the picture's a little wavy when scrolling quickly (like in Sonic), but I think that's the TV (a rather large, modern CRT TV).

[TmEE]

Can you post some pics ?

[Joe Redifer]

The solid border is normal. Most Genesis games do this. Usually you will not be able to see this as it is outside of the TV's visible scanning range (ie: overscan), but perhaps the image on your TV is slightly shifted in one direction or the other which will make this border show. Or, if you have an HDTV you might be able to see this border all around. I am not sure why this border isn't always black for every single game and instead is a solid color. Black would be much preferred. You never see movies with a bright blue letterbox.

[Mr. Ksoft]

I figured it was the overscan border... too bad I can't shift the picture to the left just a tad.

[TmEE]

MD had the ability to change the overscan color, and I will make full use of it...

[Joe Redifer]

Yes, make it black at all times unless you are doing something on purpose.

[TmEE]

I'm doing something on purpose, like fades and stuff when hit or get some item or when there's some big ass explosions...

[Joe Redifer]

Explosions might be cool. The bloom effect on CRTs would grow and shrink the picture slightly as it changed from bright to dark. Just as long as the effect isn't happening constantly (like say, every time you get hit).

[TmEE]

it will get more red when you're closer to dying...

[robrob]

Hi - Wonder if anyone can help me. When using a Scart lead on my Megadrive 1 or 2 there is a border only on the right hand side (looks like the screen is slightly off centre) Ive tried this on 2 seperate TV's both with a modded and unmodded megadrive but still get the same result. Any ideas?

Sorrry for not posting on a new thread but the unusual restrictions on the users makes it impossible.

thanks in advance

rob

[TmEE]

its how MD (and many other devices) output their sync signals... someone told me that the Hsync is triggered a bit earlier to compensate for the delay generated say in the RGB encoder... I have no idea if its true... my MDs did same (there's a small HW fix for it) and so do my Dreamcast (I haven't managed to get a good fix for it)....

PS - you need 10 posts to start a new thread...

[Joe Redifer]

When using RGB the picture will seem slightly shifted to the left. You can compensate for this with your TV's service menu, but every manufacturer has a different method to get into it and it you're not careful you can really mess up your TV as well.

It should seem perfectly centered with composite video, right?

[TmEE]

On my TV it makes no difference if I use RGB or Composite, but it does on other TVs in my family...

And I would like to get into the service menu of my TV, but all datasheets on my TV are incomplete, the chapter that has service menu stuff in it is missing.... damn. IIRC, my TV is Philips 21PT136B, it has been manually calibrated in one repair shop (as that TV was miscalibrated in factory...).

[evildragon]

I gave you the service menu codes, did it not work? I sent you a link containing a shit load for the Philips brand.

PS: Here is how the Genesis outputs it's picture via Composite. This is a non-over-scanned image.

http://img.photobucket.com/albums/v395/Evilweredragon/segacapture.jpg

[TmEE]

that black band is not part of the screen (only the blue area is), and the codes you gave me didn't work :(

[evildragon]

the black band is there, it's in their with the sync output. You won't notice it on your TV, but if you have a scope, you can.

[TmEE]

my LCD doesn't show it (which shows all there is), nor does a video capture card my brother has... MD VDP doesn't turn off RGB during a scanline.

[evildragon]

LCDs have over-scan, trust me.

Capture cards have it too. You MUST turn off the over-scan. Programs like DScaler can turn off the overscan completely, on supported cards. My screen capture is from this.

EDIT: EITHER WAY, Joe has professional equipment, he can elaborate more on this.

[TmEE]

That blue are IS the overscan...

Joe should shed some light on it...

[Joe Redifer]

I don't feel like dragging my Genesis up to capture video onto the computer right now, but yes, the blue is the overscan. Evildragon's picture is 720 pixels wide which is the standard capture resolution for DV video, so it is likely that the black bar is in there, at least for that particular scene. I've never personally seen it, but then again I've put maybe about 3 hours of my life into playing Sonic 2 since it was released and I've never done any video captures of it.

[TmEE]

that black (if it is part of the picture, not added by capture card)should be there with all games (and all systems, noticable on systems that can have custom overscan color like MD)... I'll be getting an oscilloscope soon and I'll be able to do some experiments.

[evildragon]

After some experimenting, it's there on everything, it never moves. I have not checked 256 pixel wide games though.

I'll be doing that later tonight.

For reference, here's another image I captured a while ago with the same exact setup..

http://fc07.deviantart.com/fs5/i/2004/307/b/d/Drunk_CNN_Dude__by_blackevilweredragon.jpg

The bar is only just a TINY bit there.. It'd be hard to detect on a real TV or LCD without a scope. I mean, it's black on a black screen, so you'd "think" it's not there.. It's everwhere.

[TmEE]

my TV doesn't display much of the horizontal overscan, but it does all vertical, including the few missing pixels on bottom right when MD is in 60Hz.
Anyway, I'm getting an o-scope in next week, and I can do tests... I can't really say the black is not there , it can be added by RGB encoder chip (if it really is there)... I'm unable to see any of it (using non-"proffessional" methods...) on RGB...

[evildragon]

Just remember, when trying to find a black bar on a TV screen, it's going to be hard, because it'll look like there's no scan. I think cranking the black level (brightness) might reveal it as a grey spot. I'll need to check this on my Sony PVM.

EDIT: My PVM won't let me adjust it far enough to the right. Need to find a monitor that will.

EDIT2: Yea, it's obviously not VDP created. More like, the VDP wasn't displaying anything yet at that spot, but the sync was active. That can do it...

[Sublevel]

I just recently discovered these colored borders. So the only option is to get a Genesis model 1? How exactly do you change the border colors?

[TmEE]

All MDs can have different border colors, and it all controlled by whatever runs on MD... you need to write to one VDP reg to change the color (any of currently loaded 64 colors).

Yea, it's obviously not VDP created. More like, the VDP wasn't displaying anything yet at that spot, but the sync was active. That can do it...

its not, VDP doesn't turn off RGB lines... did a small test, not too accurate though... I'll verify all when I get that o-scope next week.

[Joe Redifer]

I will try to capture some Sonic 2 video tonight. Might nap first. Long day ahead. :(

[TmEE]

I have long weekend... military related stuff...

[evildragon]

I know it can change borders. That's obvious.

You're not understanding what I'm saying. The VDP may not be outputting an overscan color at the time, but the sync was still starting that line, thus a blank black area. I mean, if no picture, it's black.

If that's still not understood, then forget it. I know what your trying to say, but you don't know what I'm trying to say. It's not like I'm on the same wavelength of communication as you.

[TmEE]

you equipment shows black because it thinks there's nothing to show, though VDP still continues to output stuff

[Joe Redifer]

The black bar is there, at least in Sonic 2 (I didn't try any other games):

http://www.joeredifer.com/crap/sonic2.png

S-video capture. My system hates capturing from the Genesis.

[evildragon]

TmEE, it shows black because it's just plain there. Everything shows it, and now Joe has proven it that it is indeed there.

[David J.]

I have long weekend... military related stuff...

Haha, I'm in the same boat....

[TmEE]

my weekend is over... I'm exhausted...

and I'll go to my friend's place after a few days, grab the scope and check myself... HBL period in MD is NOT that long... if it would, 3D with nice framerate would be much easier on MD...

[Joe Redifer]

Remember that the video is resized from whatever the Genesis outputs to 720x480. That's just the way DV works. The black bar isn't there in other sources digitized to DV. It wasn't there when I recorded Street Fighter Zero 3 on the Saturn. There was an overscan area, granted, but the picture was perfectly centered.

[TmEE]

I can make the black area appear on almost quarter of the screen (on right side) if I want (thanks to the small screen centering mod in my MD2)... and that's not what MD VDP outputs.

[evildragon]

My HDTV's scaler allows me to move the picture horizontally or verticlly.

If I move it out of the picture's sync, you'll be presented with a 30Hz flashing blue screen.

When shifted to the left, the overscan color is solid, but then goes to the no sync flashing blue.

When shifted to the right, you see the black stripe, THEN the flashing blue.

[Joe Redifer]

I imagine there is an 8 (or 16)-pixel block on the left that is masked out of Sonic 2. Many Master System games did this when they scrolled and several Genesis games do this as well when things get funky. Sonic 2 could mask this out to hide problems that might otherwise be visible. Just a weak theory. But I don't think other Genesis games output that black bar. Maybe I will test later tonight.

[evildragon]

tried knuckles chaotix, and it's still there...

[TmEE]

I imagine there is an 8 (or 16)-pixel block on the left that is masked out of Sonic 2. Many Master System games did this when they scrolled and several Genesis games do this as well when things get funky. Sonic 2 could mask this out to hide problems that might otherwise be visible. Just a weak theory. But I don't think other Genesis games output that black bar. Maybe I will test later tonight.

MD games don't need that pixel block, as there's nothing to hide (unless game is made to be so)... Sonic 2 is not one of them.

[evildragon]

even if there was a pixel block, wouldn't it be INSIDE the overscan area, not outside?

[Joe Redifer]

Yes, like whenever the Genesis tries to do it's limited rotation trick. I think TMEE is right, the black bar is not part of what the Genesis generates, but somehow makes its way into the signal.

[evildragon]

well that is what I TRIED to say, but was essentially told i was wrong. so i shifted theories.

couple pages ago: "Yea, it's obviously not VDP created. More like, the VDP wasn't displaying anything yet at that spot, but the sync was active. That can do it..."

[Joe Redifer]

The end result is that the bar IS in the video signal before it reaches the display. I've also wondered about the bottom garbage that only Sonic 2 seems to create.

[evildragon]

The colorful dots? That's on about every game.

Even the Sega CD BIOS.

Cause, last I heard, they thought it was the writing to CRAM.

[Joe Redifer]

The bottom rows of pixels aren't right... they don't match what is directly above them.

[evildragon]

oh, the 2 line bug.

yea, that was one of the things that my NES Sonic 2 hoax got caught with.

i don't know what causes it.

[TmEE]

2 line bug, most likely a simple error... like 2 last line scroll table values don't get delivered...

And the pixel garbage appears when there's anything written to VDP color palette.

[Whitesnake]

Sorry to resurrect this topic after so long but I've been recently experiencing this faint vertical line issue on my 40" LCD TV.

I'm using a Sega Nomad with RGB Scart and it is quite annoying to say the least.

The problem doesn't occur when you use the composite pin (on other Scart socket) on the RGB Scart but the picture is fairly poor that way.

This website seems to document the same problem for the Neo Geo and a fix. http://www.mmmonkey.co.uk/console/neo/video.htm

Does TmEE or anyone else have a simple straight forward fix for this problem?

Thanks :)

[TmEE]

over RGB one should not have such lines unless the cable is done wrong, there should be a 100ohm resistor going to one pin, that turns on RGB. Some cables have a wrong value resistor there and you get mix or RGB and composhit (with these lines present). See inside the SCART end, and check the resistor value.

[Whitesnake]

From what I can tell it is same as this RGB Scart.

http://members.optusnet.com.au/eviltim/gamescart/mega2.png

[Whitesnake]

Here are a couple of pictures from my LCD TV

http://img199.imageshack.us/img199/3755/image078rq.jpg
http://img80.imageshack.us/img80/2424/image076f.jpg

[JDB]

^^this was the problem i had

[Whitesnake]

^^this was the problem i had

Were you able to fix it? ;)

[Whitesnake]

Sorry to bump but does anyone have a solution to this problem?

I tried emailing the guy who runs mmmonkey.co.uk but the email failed.

[Kaze Okami]

Bumping this with a question.

I'm in the same boat with the lines and i'm confused about which resistor needs replacing. I changed the resistor to a 100ohm resistor thats linked beteen pin 8 and 16 but I get the same problem. Where am I suposed to put this resistor?

[M.U.S.H.A.]

Bumping this with a question.

I'm in the same boat with the lines and i'm confused about which resistor needs replacing. I changed the resistor to a 100ohm resistor thats linked beteen pin 8 and 16 but I get the same problem. Where am I suposed to put this resistor?

I'm having the same problem with the faint vertical banding. After finally getting around to buying an RGB SCART cable and Component Video converter, I hooked them up to my HDG Model I Genesis and noticed it right away.

So I opened up the SCART end of the cable to check the resistors, and the one going from pin 8 to pin 16 is 180 ohms.

In the meantime, I messaged the seller about the cable, and he seems to think that it's a problem with the Genesis I video encoder chip. One that he's been unable to resolve.

What do, Sega-16?
Try to replace it with a 100 ohm resistor? It seems Kaze already tried that to no effect.
On the one hand, this is the best picture I've ever seen my Genesis put out, vertical bands or not. On the other, I know that somehow it could be better...

[MEGADRIVE Jeroi]

ALL of them (MD1 and MD2, don't know about 3) support RGB.

And I got these vertical lines form my MD2 too, using RGB... I got rid of the lines by building my own composite sync out of H and V sync that MD VDP outputs (and fixed the screen shifted to left issue in the process...).

Hay man, please pm me whit pic opf this, I have with my Sega multi-mega the shifted left rgbissue and I want to get rid of it. Could you advise me?

[M.U.S.H.A.]

So, using the 100 ohm resistor had no effect. Still have the faint vertical lines.

Does anyone know if the Sync Striker would fix this problem, by cleaning up the CSync to get a pure Sync signal?

http://www.arcadeforge.de/?page_id=880#pcbonly

Might help to have a plug-and-play solution for those of us who don't want to mess with the internals of our consoles...

[Whitesnake]

So, using the 100 ohm resistor had no effect. Still have the faint vertical lines.

Does anyone know if the Sync Striker would fix this problem, by cleaning up the CSync to get a pure Sync signal?

http://www.arcadeforge.de/?page_id=880#pcbonly

Might help to have a plug-and-play solution for those of us who don't want to mess with the internals of our consoles...

I have the SyncStrike and doesn't remove the jailbars from the picture. :(

[M.U.S.H.A.]

I have the SyncStrike and doesn't remove the jailbars from the picture. :(

Yeah, I was afraid of that. I grew impatient and tried this...

http://www.assemblergames.com/forums/showthread.php?t=32194&page=3

Which actually did a good job of eliminating most of them. I discussed the results here...

http://www.sega-16.com/forum/showthread.php?7796-GUIDE-Telling-apart-good-Genesis-1s-and-Genesis-2s-from-bad-ones./page77
http://www.sega-16.com/forum/showthread.php?7796-GUIDE-Telling-apart-good-Genesis-1s-and-Genesis-2s-from-bad-ones./page78

How do you have yours set up, Whitesnake? I assume you have it hooked to a CGA-capable monitor of some kind, or to a scaler & HDTV. You say you have jailbars, but how does it look otherwise?

[Whitesnake]

Yeah, I was afraid of that. I grew impatient and tried this...

http://www.assemblergames.com/forums/showthread.php?t=32194&page=3

Which actually did a good job of eliminating most of them. I discussed the results here...

http://www.sega-16.com/forum/showthread.php?7796-GUIDE-Telling-apart-good-Genesis-1s-and-Genesis-2s-from-bad-ones./page77
http://www.sega-16.com/forum/showthread.php?7796-GUIDE-Telling-apart-good-Genesis-1s-and-Genesis-2s-from-bad-ones./page78

How do you have yours set up, Whitesnake? I assume you have it hooked to a CGA-capable monitor of some kind, or to a scaler & HDTV. You say you have jailbars, but how does it look otherwise?

I have it hooked up to a SyncStrike and that is plugged into a GBS-8220 scaler which is plugged into my Samsung SyncMaster 214T.

Although at present I can't get a stable picture with the Sega 32X.

it is shame there is no solution for this jailbar issue =[ I think it plagues every Mega Drive in RGB mode. I noticed some people say they don't get it but I'm not convinced, I'm sure they are not running in RGB or it is being masked by their TV.

I get jailbars on two different Mega Drive Model 1 revisions plus two Sega 32X revisions and a Sega Nomad.

I'm not sure about lifting PIN6 on the RGB encoder I think this just moves the problem to another part of the colour spectrum and it may cause sync issues with the Sega 32X as it uses the composite for sync.

[lumclaw]

Main issue is people assume it only affects model 1. When that's just NOT true, at all. No one bothers to do much research about it for other versions. I'm actually planning to buy someone a model 2 later to help them look into this further.