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nikoniko
Account closed
Registered: Dec 2006
Posts: 1 |
New video modes? 320x400 and 160x400
Hi all,
Hydrophilic/Hydradix over at the Commodore 128 Alive! forums has been working on a technique to achieve 320x400 and 160x400 interlaced modes on a C128, taking advantage of the VIC IIe's undocumented test bit to allow fine control of raster output. He's succeeded in getting it to work for NTSC (at least on his own TV), and has now put up a simple demonstration and instructions on fiddling with the settings. Anyway, with some experimentation it sounds like it could turn into something pretty cool, especially if some bright minds here could combine it with other techniques.
I know this place is mainly about 64 coding, but since the approach should also work on 128s in 64 mode, I thought you might like to know about it.
Here's his announcement: http://landover.no-ip.com/128/viewtopic.php?pid=2637
And here's his webpage, which goes into some detail about the technique: http://www.geocities.com/hydradix/C128/Interlace.htm
And finally, here's the original forum discussion while he was working on it: http://landover.no-ip.com/128/viewtopic.php?id=807
I believe he's tried to make it easy to tweak, so PAL support could probably be achieved by someone who wants to play with it.
I'd recommend that if you want to ask him questions, the forums I linked to are probably the best place since he's a frequent poster over there.
Cheers,
nikoniko |
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A Life in Hell
Account closed
Registered: May 2002
Posts: 204 |
hrm, interesting.... actually really cool. A shame that no-one has worked out a way to do this on a stock c64 tho. But still really cool :).
As we all upgrade to more digital stuff, i wonder if this is going to become less relevant, as most LCD tv's (YC == svideo :-p) and such like seem to turn the c64's input into a "real" interlaced mode anyhow (not supporting half lines to begin with, after all :))
EDIT: doesn't the c128 have interlaced modes on the VDC anyhow, btw? Tho the VDC lacks multicolour, so maybe that's a stupid point :) |
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PopMilo
Registered: Mar 2004
Posts: 145 |
Great trick!
I remember me and my bro did some experiments with $d030 and managed to stretch display verticaly so that 200 lines would cover entire screen :)
I know we did some "dec inc d030" at the bottom of the screen... time between dec and inc determined how big the stretch was.
it was something like "vertical overscan mode"... We even modified "wizard of wor" and played it like that...
Unfortunatelly, our c128 now boots only in 64 mode... will have to try to repair it... |
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WVL
Registered: Mar 2002
Posts: 886 |
gonna try this @ home.. the hidden powers of $d030 :P |
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Cruzer
Registered: Dec 2001
Posts: 1048 |
This can be done on a stock C64 by scrolling the picture up or down one pixel every 2nd frame. That way the eye will be moving half a pixel each frame. |
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JackAsser
Registered: Jun 2002
Posts: 1995 |
@Cruzer: We all know that the secret powers of castle Camelot can do lots of stuff, but WHAT are you talking about? :D |
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yago
Registered: May 2002
Posts: 332 |
JackAsser: Thats actually true. By scrolling up with halfspeed, you essentially get interlace. Also works with emus.
And, as Cruzed said, its nothing todo with the hardware, but with the human eye+brain.
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Steppe
Registered: Jan 2002
Posts: 1510 |
Teh brain is teh stupid!!!11
By the way, isn't that similar to what Crest did in Krestage 2? Or did they mean 640x400 DIAGONAL? |
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Style
Registered: Jun 2004
Posts: 498 |
Quetzal/Chrome had some success with this a while back. I think he's still planning to do something with it.
works well on a 1084S which seems to cope pretty well. |
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JackAsser
Registered: Jun 2002
Posts: 1995 |
Quote: Quetzal/Chrome had some success with this a while back. I think he's still planning to do something with it.
works well on a 1084S which seems to cope pretty well.
Doing true half-pixel interlace on a stock C64 is not the same as "essentially" doing it imo.
@Yago, Cruzer: The method you describes will only give the feeling of higher resolution when scrolling. For still images this method will simply only reduce to 25hz color-interlace. I.e. not actually yield any higher resolution. Or did I misunderstood what you meant? |
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yago
Registered: May 2002
Posts: 332 |
afaik, only works with (up) scrolling, otherwise you only get "more" colors, but not better resolution.
This trick with upscrolling is indeed used in many demos (for the endpart), shamefully i cant name a single one atm
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