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**amorenod** · 25-12-2009, 10:21

It doesn't seem a RGB shift problem. Both screens look like a 4:3 image aligned to the left instead of centered, without losing anything, not a biggie IMO.

**meppi** · 25-12-2009, 10:36

Ah that's right, when put in game mode the Tv automatically switches to 16:9 and you can't adjust it manually.

So I put it in normal mode and on 4:3 with another game to compare:

Same effect. Even the DC startup screen does that, although not as much as the games for some reason.
It does look like the picture is positioned to the left no matter what I try, at least when I use RGB.

Weird since every other system I have doesn't do this. (PC-Engine, Saturn, PSone, PS2, N64, SFC)

**Largo** · 25-12-2009, 10:44

if i plug my dreamcast into my panny v10 ,rgb, the signal goes ape ****, i thought it was just a dodgy cable, but now hmm

**amorenod** · 25-12-2009, 10:46

I see. For one game, I would use the 16:9 mode and forget about the service menu, scary stuff.

Grey borders, ugh, almost forces you to never use 4:3.

**meppi** · 25-12-2009, 10:54

Yeah, I'm not crazy about going in there and possibly hurting my set due to my incompetence.

The problem is that I know there are several other games as well that don't support VGA, so I would like to have a solution if at all possible.

Those grey borders, yeah. I feel the same.
I understand it's to protect your screen from burn-in, but I'd rather play a stretched game than play it like that.
I don't actually mind the stretched image in most cases.

**amorenod** · 25-12-2009, 11:12

Hard one, specially if other RGB devices work fine.

**Link83** · 25-12-2009, 11:55

Well, I have some info which may be relevant but it doesnt really help solve your problem

(Please note, I dont claim to know everything about video signals so I apologise for any inaccuracies in the following text. I have tried to make it as simple as I can, so may have 'simplified' or 'skipped over' some of the more complicated bits)

Firstly a bit of backgound info. Its important to understand that an RGB Scart connection does not simply require just the three colour signals Red, Green and Blue - you also need a synchronization signal so the TV can 'lock-on' to the RGB signals.

In RGB monitors that use a VGA connection these sync signals are called Horizontal Sync (H-Sync) and Vertical Sync (V-Sync) However when it comes to TV's these two signals were combined together into what is called Composite Sync (C-Sync) I presume this was done to reduce the number of separate wires needed for an RGB connection.

When a Composite Sync signal is also combined with picture information it then becomes Composite Video.

Now when Scart was being designed 30+ years ago the designers already knew they wanted to support Composite Video signals as well as RGB signals, so rather than have a separate wire/pin for just a C-Sync signal the Scart designers decided that they would just use the C-Sync signal that was already combined into the Composite Video signal.

However, Composite Video already includes picture information, but inside every TV there is a chip that strips/separates this picture information from Composite Video, leaving just the C-Sync signal. Your TV can then use this C-Sync signal to 'lock on' to the RGB picture signals.

So basically for an RGB Scart connection you must always have a Composite Video (Or C-Sync) signal.

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...Now onto the Dreamcast!

Usually in most games console Composite Video is always being output on the AV connector, even if you are not using a Composite Video connection. As mentioned previously, the Composite Video signal is still used by your TV when your using an RGB Scart connection, so most games consoles just leave it 'active' all the time.

However the Dreamcast is different. When connected using an RGB connection the Composite Video signal is purposefully disabled. Instead, the Dreamcast outputs a C-Sync signal to the Scarts Composite Video pin, so that the TV can still 'lock on' to the Dreamcasts RGB signal.

(The following is a bit of speculation on my part, but it makes logical sense)
Now what should be happening is that the chip inside your TV that I mentioned earlier will still try to strip the picture information from the Dreamcasts C-Sync signal, as it would normally do with a Composite Video signal. However since there is no picture information included in the C-Sync signal it should just pass the signal through untouched.

The problem is, your TV is set to expect a small delay (milliseconds) for the chip inside your TV to strip the C-Sync signal from the Composite Video signal. However the chip no longer needs this 'extra time' because the Dreamcast is already giving it a pure C-Sync signal. In effect the chip is giving the C-Sync signal to the TV faster than it expects and this results in the black bar on the side of the screen. It really depends on the TV model and internal circuitry as to how bad the delay/black bar is, and you can get completely different results from different brands/models of TV.

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So what can you do to fix it? Well in the past there were a few devices sold as 'scart shifters' (Cant find a link right now but google should help you out) That would correct the picture shift by adding/removing the C-Sync signal delay. The other possible alternative I can think of would require modding the Dreamcast to combine the H-Sync and V-Sync signals used for VGA into one C-Sync signal using an extra chip, and then hoping your TV likes the new C-Sync signal.

Finally, I thought I should mention that this problem is not just limited to the Dreamcast - if you google 'scart shift' you can find many other people who have had similar problems with a shifted RGB picture from other consoles, although these are likely due to other issues. It only takes the sync signals being slightly 'out of spec' from what the TV is expecting to get the Scart shift issue. Some TV's such as those made by Sony often offered an 'RGB shift correction' option in the TV's menu so that you could correct the shift issue manually.

Anyway, sorry for waffling on so long and Merry Christmas everyone!

**meppi** · 25-12-2009, 12:16

That certainly was an interesting read and makes lots of sense actually. Well as far as I understand how these things work.

I guess it's either finding a scart shifter, which seem to be hard to locate or use the S-Video cable instead then.

I wonder if ChaoticJelly would be able to get something like this worked out...

**Link83** · 25-12-2009, 12:38

Glad it helped a little

Another possible option (that you may already know) is that many Dreamcast games that dont support VGA can be 'tricked' to do so by flicking the VGA box TV/VGA switch just after the game starts to boot (After the Dreamcast drive goes 'beep')

Alternatively you can actually download some of the non-VGA Dreamcast games 'VGA patched' and burn them to CD-R. Although i'm not trying to condone piracy, in this instance if you own the originals I dont see the harm

**meppi** · 25-12-2009, 13:20

I've tried the trick, but couldn't get it to work though. Perhaps I need to time it better.

The CD-R option does seem like one of the only options in this case, but even though I have nearly all the games I want in original form, many times even twice or more,

(Pal+NTSC-J+spare copies) I'm not that crazy about such a solution to be honest.

S-Video looks quite good tbh, certainly not as crisp as RGB but for that handful of games that shouldn't be too much of a problem.
And seeing how the N64 version of Bangaio looks not even as sharp, it isn't that bad in retrospect.

**Lyris** · 25-12-2009, 14:34

Good old SCART. Sorry to hear of your troubles, but S-Video seems to be the best compromise here. A shame, because the DC's S-Video output isn't too pretty.

**charlesr** · 26-12-2009, 15:22

Works fine on my Panny 9 series. Sorry. I'm not helping am I.

**fallenangle** · 29-12-2009, 15:53

I'd find reliable advice on how to get into the TV's service menu and 'simply' adjust the horizontal shift. I've found having such access invaluable for adjusting picture geometry or positioning issues like this. although never so a great a one as that shown.

I think Link83's explanation sounds very plausable - quite why the DC has separate composite video and composite sync channels I've never understood. It's why a DC RGB SCART cable won't work with a non-RGB SCART TV socket too whereas all(?) other consoles (or any other external equipment) simply reverts to composite.

But, as I said, you do need to get reliable advice from somewhere like the AVForums.co.uk about accessing the service menu and especially the specific abbreviations used for your particular make/model. It's not that scary once you're in and you're certain you know which parts to adjust but there is undoubtedly an element of risk all the same.

**meppi** · 29-12-2009, 16:29

Thanks for everyone trying to help.

The last thing I tried was to see if any of the other RGB cables that were in storage would do anything different.
I know, slim chance. And the problem stayed the same.

The trouble with going into the service menu to adjust this would probably be that the other channels AV2 and AV3 would also be changed, and thus be out of synch for everything else.
Well that's what I read on AVforums.
So in the end I'm going to stick with s-video for the couple of games that don't support RGB.
It's not that bad really, especially since just about anything and everything else I throw at the tv comes out amazing looking.
Well besides NES games through composite, which look awful.

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my plasma hates Dreamcast RGB :(

my plasma hates Dreamcast RGB :(

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