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 Post subject: VGA question
PostPosted: Sat Dec 06, 2008 3:34 pm 
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I am about to chunk my old TV and just have my HDtv and a PC monitor in my room for gaming. I am going to buy a VGA adapter of course, but I have a question. Does all or most all DChomebrew and emulators support VGA, or was it just some commercial games that did not support it?

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 Post subject: Re: VGA question
PostPosted: Sat Dec 06, 2008 5:39 pm 
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It's the Dreamcast that generates the VGA, not the software. The few commercial games that are known not to support VGA would be the ones missing the VGA flag in their IP.BIN so you'll get a message and the Dreamcast refuses to boot the game. You can skip the IP.BIN check by using a boot disc or just by unplugging the cable prior booting. When plugging it back in, the Dreamcast switches to VGA.

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 Post subject: Re: VGA question
PostPosted: Sat Dec 06, 2008 7:33 pm 
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Actually there are quite a few that don't support it in software either, and will give video glitches and stuff.

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 Post subject: Re: VGA question
PostPosted: Sat Dec 06, 2008 7:51 pm 
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Interesting. - Do you know which ones that would be ?

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 Post subject: Re: VGA question
PostPosted: Sat Dec 06, 2008 7:55 pm 
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As long as nxDoom, NesterDC/NesterDC SE and beats of rage work I think i'll be happy.

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 Post subject: Re: VGA question
PostPosted: Sat Dec 06, 2008 8:21 pm 
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Christuserloeser wrote:
Interesting. - Do you know which ones that would be ?


Well, I was referring mostly to commercial games (I forgot to say that when saying 'quite a few'=> 'quite a few commercial games'), but a lot of early homebrew (and even some more modern ones) had PAL flavors that are incompatible with vga (they force 50hz and work around it). IIRC there was a release of dcdivx that was of that sort, as it also took advantage of one of the PAL only resolutions (256x256 or something like that).

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 Post subject: Re: VGA question
PostPosted: Sat Dec 06, 2008 8:31 pm 
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Nico0020 wrote:
As long as nxDoom, NesterDC/NesterDC SE and beats of rage work I think i'll be happy.


Yeah, they all work perfectly. The Dreamcast's VGA mode outputs to 640x480p60, so even low res stuff looks pretty breathtaking due to the upscan.


Quzar wrote:
Well, I was referring mostly to commercial games (I forgot to say that when saying 'quite a few'=> 'quite a few commercial games'), but a lot of early homebrew (and even some more modern ones) had PAL flavors that are incompatible with vga (they force 50hz and work around it). IIRC there was a release of dcdivx that was of that sort, as it also took advantage of one of the PAL only resolutions (256x256 or something like that).


Thing is that it seems that the Dreamcast always outputs 640x480p in VGA mode, no matter what resolution is used.

The forced 50Hz display in some European commercial games (like Code Veronica) will prevent the video from being compatible with most HDTVs, that is correct. My CRT PC monitor even accepts 640x480p50 tho.

Regarding the commercial games: Are there actually a few that will give you glitches when in VGA mode ?

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 Post subject: Re: VGA question
PostPosted: Sat Dec 06, 2008 9:03 pm 
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Christuserloeser wrote:
Nico0020 wrote:
As long as nxDoom, NesterDC/NesterDC SE and beats of rage work I think i'll be happy.


Yeah, they all work perfectly. The Dreamcast's VGA mode outputs to 640x480p60, so even low res stuff looks pretty breathtaking due to the upscan.


Which can cause exactly the glitchy. It will always try to upscale, but since so many things use mipmaps, the higher resolution causes more stress on the system. That's one example of a way that the forced vga can cause problems. The Dreamcast doesn't do this all automagically. one of the biggest issues with games in forced vga is them displaying on 1/4 of the screen. This happens because the resolution of display changes to 640x480 but all the data is designed for 320x240.

viewtopic.php?f=36&t=98100 In that topic (you posted in it...) there is reference to a site with a compatability list. http://www.racketboy.com/retro/2006/05/ ... -list.html and a number of the listed games are incompatible even with ip.bin patching.

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 Post subject: Re: VGA question
PostPosted: Sun Dec 07, 2008 7:45 am 
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Quzar wrote:
one of the biggest issues with games in forced vga is them displaying on 1/4 of the screen. This happens because the resolution of display changes to 640x480 but all the data is designed for 320x240.


I never ever experienced that. Got any example ?

Quzar wrote:
http://dcemulation.org/phpBB/viewtopic.php?f=36&t=98100 In that topic (you posted in it...) there is reference to a site with a compatability list. http://www.racketboy.com/retro/2006/05/ ... -list.html and a number of the listed games are incompatible even with ip.bin patching.


This list doesn't even mention if its based on PAL or NTSC games, they basically just label it as "English", and I doubt "Giant Killers" was released in the US. Also, 320x240 games are described as "pixelated" :roll:

I also got no idea what they mean when they say "patchable".


Nephil's list is much better: http://www.nephil.de/vga-comp.html


- Anyway, I didn't ask for some odd links, I asked for your experience with 'VGA and glitchy graphics.

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 Post subject: Re: VGA question
PostPosted: Sun Dec 07, 2008 9:52 am 
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Christuserloeser wrote:
Quzar wrote:
one of the biggest issues with games in forced vga is them displaying on 1/4 of the screen. This happens because the resolution of display changes to 640x480 but all the data is designed for 320x240.


I never ever experienced that. Got any example ?


That would most likely be the problem someone was having running ScummVM on the Dreamcast along with the game Simon the Sorcerer via VGA box, they posted on the ScummVM forum with that exact same problem and it had me scratching my head for ages trying to work out why that game only.

Christuserloeser wrote:
This list doesn't even mention if its based on PAL or NTSC games, they basically just label it as "English", and I doubt "Giant Killers" was released in the US. Also, 320x240 games are described as "pixelated" :roll:


It looks like we need a new detailed list for Dreamcast users, that in itself would be one hell of a task, you'd have to have every game to begin with, boot them all normally (record the results), try a boot disk with the ones that didn't work normally (record the results), try ripping/patching/burning the ones that didn't work (record the results)... etc. etc.

Christuserloeser wrote:
I also got no idea what they mean when they say "patchable".


I think he's referring to hex editing rather than applying a patch but I could be wrong.

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 Post subject: Re: VGA question
PostPosted: Sun Dec 07, 2008 12:29 pm 
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Christuserloeser wrote:
Quzar wrote:
one of the biggest issues with games in forced vga is them displaying on 1/4 of the screen. This happens because the resolution of display changes to 640x480 but all the data is designed for 320x240.


I never ever experienced that. Got any example ?


Happened to me a few times early on in neodc dev. Otherwise only anecdotal.



Christuserloeser wrote:
I also got no idea what they mean when they say "patchable".


Christuserloeser wrote:
MethodGit wrote:
Surely this would a catalyst for running a "backup" version of a game (instead of a GD original) as you could at least manually patch those to force VGA support?


All that's missing would be a flag in the IP.BIN bootsector, so yeah, they could be "patched" by adding this flag.


Well, since you obviously have an idea of what "patched" means, it's logical to take the meaning of patchable to be: 'able to be patched'. In this context there would also be added 'in order to achieve vga compatability'

Christuserloeser wrote:
Nephil's list is much better: http://www.nephil.de/vga-comp.html

Nephil wrote:
Blue Stinger EUR / JAP / US EUR: bedingt, Sound in Cutscenes asynchron, US+JAP: ja
It seems Nephil has also seen problems caused by forcing vga.

Christuserloeser wrote:
- Anyway, I didn't ask for some odd links, I asked for your experience with 'VGA and glitchy graphics.
I don't see that. What you asked is if I had any examples. I have examples experienced by others. What's the problem?

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 Post subject: Re: VGA question
PostPosted: Sun Dec 07, 2008 1:08 pm 
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Christuserloeser wrote:
Regarding the commercial games: Are there actually a few that will give you glitches when in VGA mode ?
Definitely. Jojo's Bizarre Adventure (US version) comes to mind; I managed to get a playable picture by maxing out the vsize knob on an old NEC Multisync (the original series that could do anything from digital CGA/EGA to analog SVGA 800x600), but even then the scrolling level had some serious artifacts on it. I think I also tried a cable swap on King of Fighters: Dream Match 1999, and it didn't bother to set up a VGA output; I'm not sure what it would do if the header were patched.

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 Post subject: Re: VGA question
PostPosted: Sun Dec 07, 2008 7:20 pm 
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Quzar wrote:
Christuserloeser wrote:
Quzar wrote:
one of the biggest issues with games in forced vga is them displaying on 1/4 of the screen. This happens because the resolution of display changes to 640x480 but all the data is designed for 320x240.


I never ever experienced that. Got any example ?


Happened to me a few times early on in neodc dev. Otherwise only anecdotal.


Interesting. Both Yabause DC and GenesisPlusDC are 320x240 and both run perfectly and in full screen in VGA.

You probably found a way to somehow deactivate the upscan... ?


Quzar wrote:
Christuserloeser wrote:
I also got no idea what they mean when they say "patchable".


Christuserloeser wrote:
MethodGit wrote:
Surely this would a catalyst for running a "backup" version of a game (instead of a GD original) as you could at least manually patch those to force VGA support?


All that's missing would be a flag in the IP.BIN bootsector, so yeah, they could be "patched" by adding this flag.


Well, since you obviously have an idea of what "patched" means, it's logical to take the meaning of patchable to be: 'able to be patched'. In this context there would also be added 'in order to achieve vga compatability'


Basically I questioned it because they don't specify what they mean exactly. - I doubt that they are referring to the missing flag in the IP.BIN, but how would we know for sure ?


Quzar wrote:
Christuserloeser wrote:
Nephil's list is much better: http://www.nephil.de/vga-comp.html

Nephil wrote:
Blue Stinger EUR / JAP / US EUR: bedingt, Sound in Cutscenes asynchron, US+JAP: ja
It seems Nephil has also seen problems caused by forcing vga.


No, it says that the EUR version has video in 25 or 50fps (for 50Hz playback), thus it wouldn't be in sync with the audio when forcing VGA (in 60Hz). They list the US/JP versions as VGA compatible.


Quzar wrote:
Christuserloeser wrote:
- Anyway, I didn't ask for some odd links, I asked for your experience with 'VGA and glitchy graphics.
I don't see that. What you asked is if I had any examples. I have examples experienced by others. What's the problem?


There's no way to verify these if certain testing conditions aren't provided. Nephil's list is pure gold for exactly that reason as it tries to list only original games (not 'patched' backups, which should work anyway) and also specifies the regional differences.




Ex-Cyber wrote:
Jojo's Bizarre Adventure (US version) comes to mind; I managed to get a playable picture by maxing out the vsize knob on an old NEC Multisync (the original series that could do anything from digital CGA/EGA to analog SVGA 800x600), but even then the scrolling level had some serious artifacts on it.


Thanks for the hint on this one. - So, the video appeared only at 1/4 of the screen ?

@DCDayDreamer: I'll look into Simon the Sorcer too.


Ex-Cyber wrote:
I think I also tried a cable swap on King of Fighters: Dream Match 1999, and it didn't bother to set up a VGA output; I'm not sure what it would do if the header were patched.


The cable swap is a really simple yet buggy solution: Plugging it back in won't get you any picture at times, but if you do advance to the next screen by e.g. skipping your game's intro, the Dreamcast will initialize the VGA out and you'll get a picture.


DCDayDreamer wrote:
It looks like we need a new detailed list for Dreamcast users, that in itself would be one hell of a task, you'd have to have every game to begin with, boot them all normally (record the results), try a boot disk with the ones that didn't work normally (record the results), try ripping/patching/burning the ones that didn't work (record the results)... etc. etc.


Yeah, but it should be worth it. The Dreamcast's VGA is one of the most amazing things this machine has to offer. I mean I always hear people claiming that the Dreamcast was way ahead of its time - and it's its VGA feature that actually was. It makes Dreamcast the only retro console that's fully HD compatible, almost a decade before 360 and PS3.

Anyway, it seems that Grimlock is getting close with his approach: viewtopic.php?p=1001774#p1001774

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 Post subject: Re: VGA question
PostPosted: Sun Dec 07, 2008 8:04 pm 
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Christuserloeser wrote:
So, the video appeared only at 1/4 of the screen ?
No; the timings were screwy, as though it were something like a mix of VGA horizontal timing with NTSC/PAL vertical timing. Even with the v-size knob maxed out, it still looked somewhat letterboxed.

More generally, I think you misunderstand how VGA support works on Dreamcast. It's not something that happens automatically; the software must configure the hardware for it (see e.g. KOS's kernel/arch/dreamcast/hardware/video.c), and it's possible for the software to get it wrong.

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 Post subject: Re: VGA question
PostPosted: Mon Dec 08, 2008 4:12 pm 
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Yeah, I don't really know how it works. I assume(d) that progressive scan (and upscanning for low res video) are activated by the hardware itself, and the IP.BIN check basically would be nothing but a software lock-out.


http://cadcdev.svn.sourceforge.net/view ... vision=611

From the comments it seems that all the interlaced settings in KOS are overriden by the VGA pin check, or upscanned when in 240p.

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 Post subject: Re: VGA question
PostPosted: Mon Dec 08, 2008 5:55 pm 
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Well, you're right that the IP.BIN check is nothing more than a software lockout. That's why you can get VGA with a cable swap or header patch in some games - the header is essentially lying about the game's VGA support. However, there are also cases where the header reflects a real lack of VGA support.

From skimming video.c it looks like KOS tries pretty hard to do the right thing, though that's not a guarantee by any means.

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 Post subject: Re: VGA question
PostPosted: Sun Jan 04, 2009 4:54 pm 
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Found a list of games that cannot be forced into VGA via the cable trick:

http://www.gamefaqs.com/console/dreamca ... 6412/36035

Quote:
NOT VGA COMPATIBLE

Games that boot with a black screen but have sound after using the switch trick
will not have a sympton in brackets.

==========
5.1 - NTSC
==========

Dance Dance Revolution 2nd Mix
Dance Dance Revolution Club Version
Jikkyou Pawafuru Puro Yakyuu
King of Fighters Evolution (~) (Resets Dreamcast after startup)
Psycic Force 2012
Rune Caster
The Psychology Game
Treasure Strike

=========
5.2 - PAL
=========

Aerowings (~) (The screen becomes overstretched horizontaly, with lines)
Bangai-O (~) (Boots to the 50/60hz selector screen, then black screen after)
Jojo's Bizarre Adventure (~) (Top half of screen only)
Plasma Sword (~) (Top half of screen only)
Railroad Tycoon 2 (~) (Occasionally it works but with effects like Aerowings)
Resident Evil Code Veronica
Sega World Wide Soccer 2000
Skies of Arcadia


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 Post subject: Re: VGA question
PostPosted: Wed Jan 07, 2009 3:22 pm 
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Add Last Blade 2 to that list.


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 Post subject: Re: VGA question
PostPosted: Thu Jan 08, 2009 7:11 am 
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Christuserloeser wrote:
Interesting. Both Yabause DC and GenesisPlusDC are 320x240 and both run perfectly and in full screen in VGA.


And nxDoom. Probably Beats of Rage as well, assuming that it has VGA support. Most homebrew uses 640x480 though.

Basically, the VGA output is a function of the Dreamcast's video output hardware. Nothing at all to do with the 3D chip or anything like that. When displaying a 320x240 screen over VGA, it uses pixel doubling (each pixel on the screen is output twice) and scanline doubling (each scanline is output twice). It just involves fiddling with a couple of registers. There are some other settings that need to be changed to get a decent signal over VGA - mostly changes to frame timing, the frame rate is changed to exactly 60Hz instead of the 59.9HZ used by NTSC and PAL60, the output is progressive instead of interlaced, and the deflicker filter is disabled.

That all needs to be set by software. KOS has different video modes for NTSC / PAL60, PAL50 and VGA. Most homebrew using KOS uses the generic video modes, which automatically switch between NTSC / PAL60 and VGA, depending on what you have plugged in. Homebrew that specifically uses PAL50 without checking (rare), or specifically uses NTSC / PAL60 without checking (even more rare) won't be VGA-compatible.

Obviously that doesn't apply to homebrew that doesn't use KOS. I have no idea what libdream (KOS's predecessor) used to do. I think libronin (DreamSNES) has VGA support. Homebrew that doesn't use any library (like Beats of Rage) may or may not have VGA support, depending on whether or not the developers added it in.

I assume Sega's SDK does the same automatic mode setting as KOS, and that the lack of the VGA-compatible flag in the IP.BIN basically means "we didn't test it" rather than "it doesn't work". The games that don't work with a VGA adapter probably did something stupid, like explicitly setting a TV display mode without checking the cable type.


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 Post subject: Re: VGA question
PostPosted: Mon Feb 09, 2009 2:03 pm 
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kohan69 wrote:
Add Last Blade 2 to that list.

Yep, and the NTSC versions of Bangai-O and Jojo's, too, and KoF: Dream Match '99 as someone mentioned above. Also The Ring and Lack of Love. I saw a list on a Japanese site once that mentioned a couple dozen games (mostly Japan exclusive releases), but I don't think I could find it again.


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