Main > Consoles

Questions on Dreamcast video

(1/2) > >>

Stormdemon:
I'm using a PAL Dreamcast on a Scart TV with a real RGB cable and I have a few doubts about some issues regarding my console. I'm asking here becasue I'm sure there are people in this forum with enough knowledge and experience to answer these questions.

When I'm using my DC on my PC monitor via VGABOX, my console is displaying 640x480 at 31khz (as indicated in the OSD of my monitor). Correct? Now, I guess this is the same frequency used in Naomi cabinets, which have Arcade mointors capable of accepting video at 31khz, right? In fact, if you stare at those monitors you cannot see scanlines, as you cannot see them in a PC monitor. I suppose the picture in those Arcade monitors is non-interlace, right? But when I use my DC on the TV with the RGB cable, the picture is interlace. I guess it's interlace because a TV cannot accept 640x480 non-interlaced, am I wrong? I also assume the signal is sent to the TV at 15khz, correct? The interesting issue is that some low res games such as Last Blade 2 or SFIII double impact display non-interlace picture (more stable display and perfectly visible quiet scanlines). Would it be possible to have this non-interlace display with 640x480 games? And why other games such as SFIII third strike, which is also low res, display interlaced picture (no quiet scanlines). Could I change it to non-interlace with some hacking to my RGB cable?

And that's all. All I'd like to know is whether I can have 15khz non-interlace display in all Dreamcast games, be it on a Scart TV or an Arcade monitor, and what do I have to do to achive this. Or at least, if anyone knows how to display the incredible SFIII third strike with the same beautiful scanlines that happen with SFIII double impact. The picture of the Dreamcast with the RGB cable is superb, but it could be even better at 15khz non-interlaced. I guess it must be possible, because otherwise, how to users of low res Arcade monitors use their Dreamcast in their cabinets? If there's any DC user who has build a cabinet with this console, please let me know what you had to do for using it with your monitor, and what kind of picture you obtain in your Arcade monitor (interlace or non-interlace).

Thank you very much.

Dave_K.:
I believe I answered this in one of your older threads.  But I'll post it again since you went to great lenghts to detail your question a second time ;D.

Arcade monitors (standard res), SCART  TVs, and normal TVs are all 15khz interlaced display devices.  There is no way to display a non-interlaced picture on these monitors.  Because of the interlaced picture (1 frame is actually drawn to the display twice as 2 fields) scanlines in the picture are sometimes very apparent (depends on the game).

VGA (640x480) 31khz, otherwise known as 480p in HDTV terminology is a non-interlaced signal.  Only high resolution arcade monitors, or HDTVs can display this non-interlaced picture.  These monitors typically have smaller dot pictches than TVs and obviously don't need to draw 2 fields per frame.  Thus this picture looks much more solid/stable.  And there are no scanline artifacts (except if the game does this on purpose...see below).

Now, when it comes to games, scanlines may be very apparent on 15khz displays.  But the game developer could also have exaggerated these scanlines in the software intentionally (much the same way MAME can simulate scanlines).  This may help the game actually play faster (it has less pixels to display per frame).  The older fighter games you mentioned happen to fall into this category.  The scanlines may be VERY apparent on 15khz displays, and also apparent on 640x480 VGA displays (via the DC VGA box).  There is no way to turn them off unless there is an option inside the game (inside the software).

So, basically there isn't anything you can do to make these games look any better unless there is an option inside the game/software options menu.  And even then, if the game allows you to "turn on/off scanlines", its not really affecting your display, but rather making the scanlines less noticable (at the cost of maybe slowing things down or making it look more pixelated/blocky).

Hope this makes sense.

giantgonzolez:
You should also ask this question at this forum, since they specialize in exactly the kind of stuff you're talking about.
http://atarilabs.com/cgi-bin/UltraBoard/UltraBoard.cgi?action=Headlines&BID=11&SID=30
BTW, I always thought that when Dreamcast was displaying 15khz RGB it was always interlaced, and when it was displying 31khz vga it was always NONinterlaced/progressive scan.
Also, here are the  pinouts and stuff for the dreamcast,
http://www.gamesx.com/avpinouts/dricas.htm
Also, some Dreamcast games just don't support noninterlaced scan/progressive scan.



--- Quote from: Stormdemon on August 02, 2003, 06:08:43 pm ---I'm using a PAL Dreamcast on a Scart TV with a real RGB cable and I have a few doubts about some issues regarding my console. I'm asking here becasue I'm sure there are people in this forum with enough knowledge and experience to answer these questions.

When I'm using my DC on my PC monitor via VGABOX, my console is displaying 640x480 at 31khz (as indicated in the OSD of my monitor). Correct? Now, I guess this is the same frequency used in Naomi cabinets, which have Arcade mointors capable of accepting video at 31khz, right? In fact, if you stare at those monitors you cannot see scanlines, as you cannot see them in a PC monitor. I suppose the picture in those Arcade monitors is non-interlace, right? But when I use my DC on the TV with the RGB cable, the picture is interlace. I guess it's interlace because a TV cannot accept 640x480 non-interlaced, am I wrong? I also assume the signal is sent to the TV at 15khz, correct? The interesting issue is that some low res games such as Last Blade 2 or SFIII double impact display non-interlace picture (more stable display and perfectly visible quiet scanlines). Would it be possible to have this non-interlace display with 640x480 games? And why other games such as SFIII third strike, which is also low res, display interlaced picture (no quiet scanlines). Could I change it to non-interlace with some hacking to my RGB cable?

And that's all. All I'd like to know is whether I can have 15khz non-interlace display in all Dreamcast games, be it on a Scart TV or an Arcade monitor, and what do I have to do to achive this. Or at least, if anyone knows how to display the incredible SFIII third strike with the same beautiful scanlines that happen with SFIII double impact. The picture of the Dreamcast with the RGB cable is superb, but it could be even better at 15khz non-interlaced. I guess it must be possible, because otherwise, how to users of low res Arcade monitors use their Dreamcast in their cabinets? If there's any DC user who has build a cabinet with this console, please let me know what you had to do for using it with your monitor, and what kind of picture you obtain in your Arcade monitor (interlace or non-interlace).

Thank you very much.

--- End quote ---

b3atmania:

Using SCART (RGB) you always get an interlaced picture. There's no way around this I'm affraid.

Some high-end European TV sets can handle non-interlaced signals. These have either component (separate Y/Cb/Cy signals) or VGA inputs. These are also common on projection equipment.

Disregard the HDTV remarks by Dave K. as HDTV is non-existant in Europe.

Stormdemon:
Dave, I think you have not understand my questions and I must say I have to disagree with many of the things you are saying. I'm sure you can have non-interlaced display in a SCART TV or an Arcade monitor. In fact, the scanlines I'm talking about are not software simulated scanlines and actually happen when you have a non-interlaced display with low horizontal rates. See for instance the difference of the picture of Windows in an Arcade monitor at 640x288 (non-interlaced) and the same picture at 640x480 (interlaced). With the first resolution the picture is as stable as on a vga monitor. The same stability can be seen in MAME when you use lower res modes at 15khz. Then you can even notice scanlines, not only because of the 15khz but because the resolution is really low. When it comes to the Dreamcast, the point is that it seems that most games display interlaced, but a few display non-interlaced. I'm sure the scanlines in SFIII double impact are not simulated and I'm sure I have non-interlaced display with this game. Launch the game with a VGAbox and you will see no scanlines at all. Of course you can have non-interlaced display using scart, not only with DC but also with PC.

Navigation

[0] Message Index

[#] Next page