Discovered something odd recently Time Stalkers (Dreamcast)

[Fusion916]

It seems if you use RGB mode, it outputs at 31KHz no matter what. I have never seen a game like this. There is a 15KHz/31KHz pin on the Dreamcast port to select between the two modes, and every game I have played uses this mode (it will even line double games that run in 240p like MVC1).

Yet even if you select 15KHz mode on Time Stalkers, it will play in 31KHz only. The boot screen will actually start in 15KHz, then switch to 31KHz when the game starts.

[fernan1234]

This is one of a bunch of DC games that force 31khz when not using specifically S-video or composite via software flags, so it's not possible to get 15khz RGBHV even with a modified cable or VGA box. As a rare 480i fan I discovered this painfully a while ago with Eternal Arcadia. There's supposed to be ways to hack the image to bypass this, but after trying a bunch of methods I was never able to figure it out.

[Syntax]

Dreamcast has 2 physical mode settings for 15k from the av port. Make sure you try both

[Fusion916]

This is one of a bunch of DC games that force 31khz when not using specifically S-video or composite via software flags, so it's not possible to get 15khz RGBHV even with a modified cable or VGA box. As a rare 480i fan I discovered this painfully a while ago with Eternal Arcadia. There's supposed to be ways to hack the image to bypass this, but after trying a bunch of methods I was never able to figure it out.

480i fan? LOL yes thats pretty rare. Interlaced video is fine for movies, but it's really hard to play interlaced games. No much choice if you want to play games form this era though....

But back on topic, I guess it was just me who didn't know there were any games that forced 31KHz. Is this exclusive to DC? I guess DC is kind of an outlier console that actually supported VGA (RGBHV, not SCART) without any mods. Assuming this VGA port was going to be hooked to a monitor I guess it was "safe" to force 31KHz.

[Fusion916]

Dreamcast has 2 physical mode settings for 15k from the av port. Make sure you try both

Which pin? There is only 1 pin for 15khz and 1 pin for 31khz. Selecting the 15khz mode has no effect. It forces 31KHz once the game is loaded past the DC boot screen.

[fernan1234]

The pin won't make a difference for games like this. I use a VGA cable with the 31khz pin lifted (pin 6 or 7, not sure), to get RGBHV 15khz on everything, except these games with the stupid software flags. Skies of Arcada for example (except PAL) will boot at 31khz, but if you go into the in-game internet browser it will switch to 15khz.

480i fan? LOL yes thats pretty rare. Interlaced video is fine for movies, but it's really hard to play interlaced games. No much choice if you want to play games form this era though....

Yep I'm weird like that, but I think it looks better than progressive on my multisync CRT, not sure why, everything just looks more organic and with more depth. I'll take the combing trade off.

[nmalinoski]

Dreamcast has 2 physical mode settings for 15k from the av port. Make sure you try both

Which pin? There is only 1 pin for 15khz and 1 pin for 31khz. Selecting the 15khz mode has no effect. It forces 31KHz once the game is loaded past the DC boot screen.

The way this is worded, it makes it sound like only one pin needs to be grounded to trigger 31kHz, but, according to my normal source for this sort of information, my understanding has been that both pins 6 and 7 need to be grounded for 31kHz to be activated (and it's not clear what would happen if only pin 6 were grounded).

[Josh128]

This is one of a bunch of DC games that force 31khz when not using specifically S-video or composite via software flags, so it's not possible to get 15khz RGBHV even with a modified cable or VGA box. As a rare 480i fan I discovered this painfully a while ago with Eternal Arcadia. There's supposed to be ways to hack the image to bypass this, but after trying a bunch of methods I was never able to figure it out.

I too am a fan of Skies of Arcadia. I have a DC RGB cable, but never ran across this issue. It looks brilliant in 480p VGA, I dont remember if I ever used the SCART RGB cable for that title. Do you not have a 480p capable display?

[fernan1234]

I too am a fan of Skies of Arcadia. I have a DC RGB cable, but never ran across this issue. It looks brilliant in 480p VGA, I dont remember if I ever used the SCART RGB cable for that title. Do you not have a 480p capable display?

You didn't have any problems precisely because it always does what you wanted it to do, which is to give you a 480p image whenever using a VGA cable. My display is 480p capable, but me being a weirdo I wanted 480i RGB, which I can get from pretty much all games using a cable with the 31khz pin lifted, but this game will still force 480p regardless. If you do use the SCART RGB cable it will do the same. Only the PAL version can do 480i via RGB, but at 50hz, though there is a 60hz patch for it.

[Fusion916]

Yep I'm weird like that, but I think it looks better than progressive on my multisync CRT, not sure why, everything just looks more organic and with more depth. I'll take the combing trade off.

I think you're just more of a fan of a soft image. On low resolution texture games with very little hardware anti-aliasing, I suppose interlaced image can look a bit more pleasing to the eyes.

Until you play a RPG where you need to read a lot of text....

But for example games like Soul Calibur on DC look great even in 480i.

[Syntax]

https://gamesx.com/wiki/doku.php?id=av:dreamcastav

Please read the usage notes
Ground both for 31k
Ground either for 2 different types of 15k

[Fusion916]

Ground either for 2 different types of 15k

This statement doesn't even make sense, unless the "two difference types" you mean is 15KHz non-interlaced and 15KHz interlaced. Even so, I don't think it's possible to force non-interlaced on everything. The DC Menu and bootscreen itself is always interlaced in 15KHz mode.

[Syntax]

Oh so you've tried it?

[Link83]

Dreamcast has 2 physical mode settings for 15k from the av port. Make sure you try both

https://gamesx.com/wiki/doku.php?id=av:dreamcastav

Please read the usage notes
Ground both for 31k
Ground either for 2 different types of 15k

I'm not certain there really is a second 15kHz RGB mode (Or if there is, it wasn't defined as such by Sega) I searched through the Dreamcast SDK some years ago and found a few mentions of the '4th mode':-



Note that in the above two charts the middle two modes have been switched around (Top chart "ON"=GND, Bottom chart "0"=GND)

And this page shows what gets reported to software when using the 'syCblCheckCable' function:-


So between the three charts you have "Undefined", "VBS/Y+S/C" and "SEGA RESERVED" all listed as the '4th mode'.

I have debated removing those lines from the gamesx wiki for years, but since I haven't actually tested the '4th mode' myself I didn't feel confident enough to remove it.

It would be great if someone could test what video signals are actually generated in the '4th mode', and what effect this has on software since the 'syCblCheckCable' function was apparently changed in different SDK revisions:-

NOTE: SCART Compatibility for European Software
SHINOBI USERS: To ensure compatibility with RGB cables, which is completely essential for European software, please switch to the new syCblCheck()shinobi function. Correct implementation of this is shown below in the Extended PAL mode section.

So I guess the results could vary from title to title?

[Syntax]

Game SX has always been my go to place for detailed pinouts of console AV ports,
but I was recently caught out by the site when attempting to build a VGA cable for a portable Wii mod im doing..

The Wii pinout there states the Wii has 2 MODE pins, but this is incorrect.

There is only 1 mode pin, Pin 8.

Pin 10 is 3.3v, id very much like them to fix that misinformation.

https://gamesx.com/wiki/doku.php?id=av: ... _av_pinout

[Fusion916]

I really these charts would reflect useful information. Just stating "RGB" and "VGA" is ambiguous. VGA is RGB. I'm guessing what they really mean is 15KHz and 31KHz.

And again its redundant to have two 15KHz modes, unless there are really forcing some kind of "always interlaced" mode vs "software selectable" or something.

[nmalinoski]

I really these charts would reflect useful information. Just stating "RGB" and "VGA" is ambiguous. VGA is RGB. I'm guessing what they really mean is 15KHz and 31KHz.

That's unfortunately how the language evolved--"RGB" being shorthand for 15kHz RGBS, and "VGA" for 31kHz RGBHV--even though they're both RGB; and "VGA", where the Dreamcast is concerned, is not actually VGA, and it doesn't help that the AV breakout boxes are often referred to and marketed as "VGA boxes".

Even if it's incorrect, I don't think any of us is really going to change peoples' labeling habits, because it seems to be good enough for many.

[Fusion916]

Unfortunately you're right. Either way, interesting thread with new information, at least for me.

[Taiyaki]

Yes I had found out about this the hard way as well. Both Time Stalkers (Climax Landers in Japan) and Skies of Arcadia do not work through RGB (even with the Retro Access scart cable that forces 15khz when switched to that setting).

I had read somewhere that you can patch the two games, make copies, and they should work. However I've never been able to find these so called patches, or patched iso's. So sadly if one wants to play those two games one has to pull out an S-Video cable, and play with less good colors (assuming calibration was done for component) and possibly off center (again if horizontal position was calibrated for scart use). A bummer, but a reason to hold on to good s-video cables for the DC.

[fernan1234]

Yes I had found out about this the hard way as well. Both Time Stalkers (Climax Landers in Japan) and Skies of Arcadia do not work through RGB (even with the Retro Access scart cable that forces 15khz when switched to that setting).

I had read somewhere that you can patch the two games, make copies, and they should work. However I've never been able to find these so called patches, or patched iso's. So sadly if one wants to play those two games one has to pull out an S-Video cable, and play with less good colors (assuming calibration was done for component) and possibly off center (again if horizontal position was calibrated for scart use). A bummer, but a reason to hold on to good s-video cables for the DC.

I spent quite a bit of time trying different old tools and methods to modify the ISO to get around this a while ago, and everything failed to work on a GDEMU. Maybe burning the modified ISO to a disc would have worked, but I didn't try that.

But the easiest solution for the handful of games that have this quirk, especially when using a GDEMU, is to use one of those cheap Extron scan converters (such as VSC500 or 700) that takes "Computer" inputs and converts them to 15khz RGB, as well as S-video and composite. On a VSC 500 and the lowest flicker filter settings RGB 480p down scanned to RGB 480i looked great, almost identical to native 15khz RGB from the DC. But I didn't test this extensively as I got lazy and just ended up settling for 480p to play these.

[Taiyaki]

I spent quite a bit of time trying different old tools and methods to modify the ISO to get around this a while ago, and everything failed to work on a GDEMU. Maybe burning the modified ISO to a disc would have worked, but I didn't try that.

But the easiest solution for the handful of games that have this quirk, especially when using a GDEMU, is to use one of those cheap Extron scan converters (such as VSC500 or 700) that takes "Computer" inputs and converts them to 15khz RGB, as well as S-video and composite. On a VSC 500 and the lowest flicker filter settings RGB 480p down scanned to RGB 480i looked great, almost identical to native 15khz RGB from the DC. But I didn't test this extensively as I got lazy and just ended up settling for 480p to play these.

That requires an Extron in the setup, not ideal, but good to know that that works.

I have yet to find a way to get patches to work on original hardware via discs either. Ideally someone who has found a way to get the patch to work could share the technique with the rest of us. Doing some research back when I was trying to get this to work I had found a message board where a user had managed to patch the game get it to run, but he didn't share the secret, and the post was over a decade old on a board that no longer had any activity.

[darcagn]

I'm not certain there really is a second 15kHz RGB mode (Or if there is, it wasn't defined as such by Sega) I searched through the Dreamcast SDK some years ago and found a few mentions of the '4th mode':-

Note that in the above two charts the middle two modes have been switched around (Top chart "ON"=GND, Bottom chart "0"=GND)

And this page shows what gets reported to software when using the 'syCblCheckCable' function:-

So between the three charts you have "Undefined", "VBS/Y+S/C" and "SEGA RESERVED" all listed as the '4th mode'.

I have debated removing those lines from the gamesx wiki for years, but since I haven't actually tested the '4th mode' myself I didn't feel confident enough to remove it.

It would be great if someone could test what video signals are actually generated in the '4th mode', and what effect this has on software since the 'syCblCheckCable' function was apparently changed in different SDK revisions:-

NOTE: SCART Compatibility for European Software
SHINOBI USERS: To ensure compatibility with RGB cables, which is completely essential for European software, please switch to the new syCblCheck()shinobi function. Correct implementation of this is shown below in the Extended PAL mode section.

So I guess the results could vary from title to title?

I have tried it before, this was around 2013 though, so my memory is hazy, I accidentally wired up a custom DC->Framemeister cable incorrectly. The cable had a toggle switch for 31KHz/15KHz, so I didn't use the 15Khz mode often, and I don't know for how long I had it wired incorrectly, but if my memory is correct, everything worked as I would have expected (meaning I got 15khz rgb) until I one day I tried an unlicensed indie game based on KallistiOS, and KallistiOS did not initialize the video correctly. I believe at this point I told BlueCrab and he patched KallistiOS to work with this configuration (I think?) to mimic the same behavior I experienced in Katana-based software, but that would mean only KOS-based homebrew made in last 5 years would display properly.

Moral of the story, I would not recommend telling anyone "Ground either for 2 different types of 15k" -- one will cause problems, the other one will not.

[Josh128]

and "VGA", where the Dreamcast is concerned, is not actually VGA, and it doesn't help that the AV breakout boxes are often referred to and marketed as "VGA boxes".

Even if it's incorrect, I don't think any of us is really going to change peoples' labeling habits, because it seems to be good enough for many.

Why would you say the DC's "VGA" is not VGA? Because its not a DE-15 connector on the console output? Because outside of that, it pretty much fits the bill.

[nmalinoski]

Why would you say the DC's "VGA" is not VGA?

Because the video output is DTV 480p (I think specifically 640x480 in 720x480 frames), which, to my understanding is not a video mode or approach covered in the VGA spec.

"VGA" normally refers to the VGA hardware capability specifications, but it can also be shorthand for the cables or the 640x480 video mode, depending on context. Based on that, I think it would be fair to say that most Dreamcast breakout boxes use VGA cables, but not the VGA video mode or VGA as a whole.

[Fusion916]

Why would you say the DC's "VGA" is not VGA?

Because the video output is DTV 480p (I think specifically 640x480 in 720x480 frames), which, to my understanding is not a video mode or approach covered in the VGA spec.

"VGA" normally refers to the VGA hardware capability specifications, but it can also be shorthand for the cables or the 640x480 video mode, depending on context. Based on that, I think it would be fair to say that most Dreamcast breakout boxes use VGA cables, but not the VGA video mode or VGA as a whole.

I think anything that displays as 640x480 progressive at 60Hz is considered VGA which is what the DC outputs in 31KHz mode. Plus I have never had an issue not being able to sync DC VGA output to any VGA monitor.

[Link83]

Its not strictly standard VGA specification. To quote chriz2600's DCHDMI github:-
https://github.com/chriz2600/DreamcastH ... ntation.md
2. Video
The dreamcast is generating 720x480p (not VGA) according to EIA-CEA-861-D "720x480p @59.94/60 Hz (Formats 2 & 3)" (chapter 4.5), not "640x480p @59.94/60 Hz (Format 1)" (chapter 4.2), but uses only 640 pixels of the possible 720.

Also these links might help:-
viewtopic.php?f=6&t=59339&p=1248481#p1248481
https://rawgit.com/chriz2600/DreamcastH ... video.html

[orange808]

Why would you say the DC's "VGA" is not VGA?

Because the video output is DTV 480p (I think specifically 640x480 in 720x480 frames), which, to my understanding is not a video mode or approach covered in the VGA spec.

"VGA" normally refers to the VGA hardware capability specifications, but it can also be shorthand for the cables or the 640x480 video mode, depending on context. Based on that, I think it would be fair to say that most Dreamcast breakout boxes use VGA cables, but not the VGA video mode or VGA as a whole.

I think anything that displays as 640x480 progressive at 60Hz is considered VGA which is what the DC outputs in 31KHz mode. Plus I have never had an issue not being able to sync DC VGA output to any VGA monitor.

It's not proper VGA. It's pillarboxed. You're getting a "VGA" output inside of a 480p DTV signal.

[Fusion916]

Its not strictly standard VGA specification. To quote chris2600's DCHDMI github:-
https://github.com/chriz2600/DreamcastH ... ntation.md
2. Video
The dreamcast is generating 720x480p (not VGA) according to EIA-CEA-861-D "720x480p @59.94/60 Hz (Formats 2 & 3)" (chapter 4.5), not "640x480p @59.94/60 Hz (Format 1)" (chapter 4.2), but uses only 640 pixels of the possible 720.

Also these links might help:-
viewtopic.php?f=6&t=59339&p=1248481#p1248481
https://rawgit.com/chriz2600/DreamcastH ... video.html

That thread has interesting information, thanks.

So the Dreamcast actually outputs 720x480 which is not VGA standard.

[fernan1234]

So the Dreamcast actually outputs 720x480 which is not VGA standard.

It does look like the actual game picture is 640x480 within a 720x480 frame when outputting 31khz RGBHV. In contrast, when outputting 15khz RGBHV the game picture is actually 720x480 (which IMO looks like the better aspect ratio for most game content).

[Fusion916]

So the Dreamcast actually outputs 720x480 which is not VGA standard.

It does look like the actual game picture is 640x480 within a 720x480 frame when outputting 31khz RGBHV. In contrast, when outputting 15khz RGBHV the game picture is actually 720x480 (which IMO looks like the better aspect ratio for most game content).

Yes just black space in between it seems.

Strange they would squish the aspect ratio to fit 640x480 screen at 31KHz.