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Video card with 240p TV-Out

 
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Yuan



Joined: 20 May 2004
Posts: 11

PostPosted: Tue Sep 02, 2008 11:14 pm    Post subject: Video card with 240p TV-Out Reply with quote

Not sure if this is the right place to ask/suggest it, but I couldn't really think of anywhere else right now.

Here's the story: While developing www.wind-water.net for the Dreamcast, I really fell in love with the "240p" display mode the Dreamcast (or Wii for VC) can broadcast.

Previously, we used regular TV-Out with S-Video to test it on TV, out of a pretty oldie NVidia card, and while I had some control over it (like the overscan area, etc.) with certain tools, it can only display 480 interlaced video (on NTSC, of course).

I believe kyuusaku is (as well as others here) very knowledgeable on the subject.

Is it possible to make a Video card (or software for existing ones) that can enable 240p and more control on the overscan, etc.? Isn't 240p just a very slight "tweak" in the signal?

S-Video on my NVidia is incredible, almost comparable to RGB. The color encoding is much better than regular S-Video on consoles, and artifacts are NOT noticeable even on a good monitor (they're probably still there, but I could NOT notice them). (Before anyone says I don't know the difference I have RGB arcade monitors and I know the image quality).

Doing some tests and making a "pseudo 240p" (by adding a black frame every 30th of a second) I noticed that higher and lower (horizontal) resolutions can look remarkably sharp even if a strong filter is applied. That way 1024*240p with a very slight filter can house most low resolutions almost the same as the real thing (though it would be great if true multi-resolutions are supported)

Better yet, if Component Video support would be added, it would be an excellent replacement for RGB (which is hard to get in the Americas). And it could still have RGB for SCART or arcade monitors.

I think it would be a product/software many ppl would want. I for one would love to my see lo-res games the way they were intended to, as well as other computer games like Cavestory or Guardian of Paradise.

Other ppl probably would love to use it on emulators, MAME projects, and whatnot.

Just a thought on a product I would really like to have (and I think it is useful). If anyone is interested, I can post some illustrative pictures and explain some things better.

Keep up the great work! I love your products. Now I think I officially count as a "Tototek collector" Very Happy
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kyuusaku



Joined: 26 Jul 2003
Posts: 941
Location: .ma.us

PostPosted: Wed Sep 03, 2008 3:06 am    Post subject: Reply with quote

Yeah, 240p is the same as 480i but the same even or odd field is sent over and over again.

And as you suspected since video cards these days are very programmable, 240p can be enabled on many cards just with a driver hack. Here's a program that helps you do that: http://community.arcadeinfo.de/showthread.php?t=8170

If you use Linux, you can add 240p pretty easily by just entering your own custom Xfree86 mode.

There's also a special video card that should make this really easy:
http://www.ultimarc.com/avgainf.html
I don't know how authentic the video is but I've heard really good things.

The only problem I see with using existing video cards is I don't think they all have the ability to generate arbitrary pixel clock rates accurately so the pixel aspect ratio won't always be console perfect, but you can mess with the monitor's horizontal size to fake it. Also maybe I'm wrong and many videocards do have very high quality frequency synthesizers, but this information isn't well published.

Also I should say that it may be possible to output component video over VGA on some cards in software (hardware accelerated via the GPU). But if you're displaying your own game, it's DEFINITELY possible on any video card with as little as a resistor if your card can be set to output composite sync which I've heard many can. In software, when rendering your RGB pixels, just transform them to YUV via a lookup table, and the values appearing on the RGB lines will be as accurate as any fancy transcoder. The last step would be to mix in composite sync on the green (now luminance) line with a resistor and connect RCA jacks.
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Yuan



Joined: 20 May 2004
Posts: 11

PostPosted: Wed Sep 03, 2008 10:39 pm    Post subject: Reply with quote

Thank you very much for your reply.

Well, since I don't have that much time to pry open anything and I'm terrible at electronics (even though in this case it's as easy as building a LEGO), I guess I was just looking for a practical way to hack the S-Video out in laptops, video cards, etc., or buy a ready card.

Something like "240p" out of the box for dummies.

I had seen the approaches you mentioned, but hadn't really got the time to tamper with them right now.

Thanks for the info.
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kyuusaku



Joined: 26 Jul 2003
Posts: 941
Location: .ma.us

PostPosted: Thu Sep 04, 2008 3:47 am    Post subject: Reply with quote

Perhaps the software hack will work on some cards with S-video too, but I'd guess that S-video and composite are generally hardwired for 480i.. Maybe ArcadeVGA can output 240p via S-video, I'd hope so since that's such an important feature.
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Yuan



Joined: 20 May 2004
Posts: 11

PostPosted: Mon Sep 15, 2008 8:37 am    Post subject: Reply with quote

I've tried to look for several solutions, none of them really practical at all.

I have another (potentially silly) question:

Is it possible to convert an already output signal from interlaced to progressive in an easy way?

Like connecting an S-Video feed to some little board that does something magical like changing the sync and outputting it in progressive mode on the other side?

Our world is so full of evolution mistakes. This should be something extremely simple to implement in any TV-Out card/device, yet seems that nobody does it natively except the Dreamcast/Wii/Vintage game consoles.

Sigh... I think the AVGA doesn't have any NTSC stuff. Not sure though.
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kyuusaku



Joined: 26 Jul 2003
Posts: 941
Location: .ma.us

PostPosted: Mon Sep 15, 2008 4:49 pm    Post subject: Reply with quote

The easiest way to convert interlaced to progressive is to get a deinterlacer, but these are really expensive. You'll also have to pre-interlace your video if you want it to deinterlace correctly. If you can't find a videocard that has programmable S-video, maybe it'd be best to just get a RGB->NTSC encoder, and use the card's programmable RGB. Personally, I view 240p on my VGA monitor (not using my computer's videocard, but FPGA) by doubling the pixel frequency so the horizontal frequency is in spec. This will work on videocards too if they can handle 320x240 @ 120hz (or 100hz for PAL games).
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