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PostPosted: Fri Jan 20, 2017 7:01 pm 
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Location: Australia, the land of British 50hz and obscure sports games.
Hello, as many of you know PAL consoles have borders due to squeezing a smaller resolution NTSC video inside a PAL TV and this can be at varying sizes depending on what TV you use. I was lucky and found a CRT that only has about half an inch of bordering on the top and bottom when used with my PAL NES. Here's a picture to scale:
Attachment:
File comment: PAL NES border example
Photo on 21-1-17 at 11.44 am.jpg
Photo on 21-1-17 at 11.44 am.jpg [ 211.6 KiB | Viewed 961 times ]


So everything's good right? not so much. I got a SNES and SD2SNES for Christmas and when i go hook it up to the same TV, the bordering is much worse than the NES:
Attachment:
File comment: PAL SNES BORDERING
Photo on 21-1-17 at 11.56 am.jpg
Photo on 21-1-17 at 11.56 am.jpg [ 211.56 KiB | Viewed 961 times ]


So can someone explain to me how a more advanced system with a higher resolution looks more bordered on my TV? It simply makes no sense.


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PostPosted: Fri Jan 20, 2017 7:09 pm 
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NTSC NES always draws 256x240. PAL NES draws 252x239.

SNES can either draw 256x224, or 256x239, depending on what the game requests. So most games use the mode with lower vertical resolution, and those extra 15 missing scanlines are why it looks letterboxed.

You should be able to use your TV's service menu to stretch things out vertically.


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PostPosted: Sat Jan 21, 2017 12:05 am 
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In case you're wondering, this is because you can't see more than about 224 lines on an NTSC set, sometimes less, so developers tended to choose DMA bandwidth over... well, nothing really; there's no benefit to overscan mode on NTSC.

Obviously there is a benefit on PAL, and since the DMA bandwidth is massively larger due to the much longer VBlank, a game that works at 256x224 NTSC (leaving room for ~6 KB of DMA per frame) will also work at 256x239 PAL (nearly 12 KB per frame). But games tended to not be heavily modified for PAL territories, so you get games with worse letterboxing than necessary.

TR3KT wrote:
a more advanced system with a higher resolution

Technically the SNES can output at 512 pixels wide (backgrounds only; sprites display at normal resolution) and/or interlaced 448/478 lines high (both backgrounds and sprites). Most games didn't, since given the limited DMA/VRAM/PPU capabilities it was usually possible to do much richer and more interesting graphics at the normal resolution.


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PostPosted: Sat Jan 21, 2017 10:14 am 
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The only widespread game from the Super NES's commercial era (1998 and earlier) that used 512x448 in-game was RPM Racing. The mode is conspicuous by its absence from the sequel Rock n Roll Racing, which used "normal" resolution.

Why not 512px wide?
Except for dialogue and text, particularly in Japanese, a 512px wide background didn't provide much of an advantage over an antialiased 256px wide background over a composite video connection. In addition, mode 5 lacked a layer compared to mode 1, and the sprite layer was always 256px wide anyway.

Why not 448/478px tall?
Interline twitter artifacts limited the amount of fine detail in interlaced graphics, making the increased video memory requirements not worth it. Doubling vertical resolution would have been more useful for mode 7 floors, as the virtual camera could be moved half a line down every other field. But for some reason, developers never thought of this.

Why not 224 in NTSC and 239 in PAL? PAL has enough video memory bandwidth for this.
The biggest problem with this is 32x32 pixel sprites. Place one close enough to the bottom of a 239-line screen and it'll wrap around to the top. To display correctly, it'd need to be split into two 16x16 pixel sprites. The other is that many background scrolling engines were designed around there being more than one invisible row of tiles at the vertical scroll seam. They'd need to be reengineered to make more, smaller uploads. And with Amiga gaming as popular in Europe as it was during the Super NES and Genesis era, developers didn't find it worthwhile to devote this much effort to a smaller market.


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PostPosted: Sat Jan 21, 2017 1:17 pm 
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tepples wrote:
The only widespread game from the Super NES's commercial era (1998 and earlier) that used 512x448 in-game was RPM Racing.

Air Strike Patrol also uses 512x448 for mission briefings and the Command HQ screen, because of course it does. (No idea how widespread/popular it was compared to RPM Racing, though.)

[edited out dumb early-morning comment about mode 7/interlace]


Last edited by Revenant on Sat Jan 21, 2017 1:39 pm, edited 1 time in total.

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PostPosted: Sat Jan 21, 2017 1:21 pm 
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Which is why he suggested moving the camera on every field so that mode 7 + interlace would produce a higher resolution image.

That seems plausible to me. Making a super-simple test ROM "should" just be a matter of calculating two HDMA tables for even and odd fields ... and coming up with something where the interlacing would make it look better, rather than just flickery.

(Given that we already know we can change all of the Mode 7 parameters on a scanline basis, we surely can change them on a field basis)


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PostPosted: Sat Jan 21, 2017 1:38 pm 
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Right, I had a bit of a caffeine-free brainfart and forgot that the interlace bit has to take full effect in every mode in order for sprite interlacing to work, so disregard that.


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PostPosted: Fri Mar 31, 2017 2:46 am 
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Bump this topic for anyone still attached.

Is there any documentation on which games use the specialised resolution and which ones don't? What about the PAL-exclusive Asterix SNES games? the they're the most likely to use expanded resolution, right?

What about other PAL-exclusive SNES games? (that i can't think of off the top of my head right now).

But for PAL-exclusive NES games most, if not, all use the extra 16 'Unviewable' pixels of resolution. Some games like Noah's Ark look very squished on NTSC consoles.


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