Pocket Heaven

karl_oz · Member Joined: 03 May 2009 Posts: 5

First of all: Thanks for this wonderful emulator and all the effort you've put into so far! I don't know anything about coding such a thing, still there's just this one issue I'd really love to see in future releases:

I understand that the GameGear's graphical resolution is 160x144 pixels (which equals an aspect ratio of 3,3 : 3)? And that's why the emulator uses this resolution, when ROMs are compiled as GameGear ROMs, right? Well, still the original GameGear hardware had a display with an aspect ratio of 4 : 3. Compare this video http://www.youtube.com/watch?v=HMkbyHEcBsU to an SMSAdvance emulated version of Sonic1 on your GBA. The horizontal scaling is originally wider than in SMSAdvance.

So, my question is simply: Wouldn't it be possible to stretch/scale the GameGear specific resolution of the emu to let's say 192x144 pixels, so it matches 4:3 and thus delivers better playability?

Dwedit · Posted: Sun May 03, 2009 2:58 pm Post subject:

It wouldn't work very well, you'd end up with pixels being scaled like AABCDDEFGGHI, every third pixel being doubled, looking really ugly.
Filtered scaling is out of the question since this uses the GBA tilemap hardware to run.
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karl_oz · Member Joined: 03 May 2009 Posts: 5

I see. So... there is no chance that this feature could be implemented properly someday? How did the actual GameGear achieve this stretching - do you know?

Dwedit · Posted: Sun May 03, 2009 7:49 pm Post subject:

I'd guess it just simply used wider pixels.
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tepples · Posted: Wed May 06, 2009 9:18 pm Post subject:

I wonder whether the intended pixel aspect ratio was 8:7 like on the NTSC SMS and NES.[1] It's too bad I don't know Z80, or I'd try writing something like the "tvpassfail" test I wrote for the NES. How do SMS games played through the adapter look on the Game Gear?

[1] This page explains why making each pixel two-thirds of a color subcarrier cycle wide results in 8:7 PAR.
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Vague Rant · Posted: Thu May 07, 2009 3:19 am Post subject:

Not sure of how they came to this decision, but Kega Fusion displays Game Gear games at 200*144, which is slightly wider than 4:3 (closer to 7:5). Forces 200*144, even; there's no way to make it display a 160*144 image so far as I can tell.
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FluBBa · Moderator Joined: 14 Feb 2004 Posts: 2048 Location: GBG

Not knocking down your efforts tepples, but you do know that there are more information per scanline than just the actual picture?
With a sampling frequency of 135/11MHz you get get somewhere around 778 "pixels" per scanline (135M/11/30M/525), of those 640 are picture (~82%).
So you have to take that into acount when you compare it to the NES.
Don't we all know that the NES PPU has 340 clocks per scanline (the cpu a third of that)? So the NES picture takes up ~75% of the scanline.
On the SMS it has 342 pixelclocks per scanline, so that also gives ~75%.

Here you can read a bit more about the scanline timing. It gives a maximum amount of ~83% picture.
http://www.batsocks.co.uk/readme/video_timing.htm
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tepples · Posted: Thu May 07, 2009 5:43 pm Post subject:

FluBBa · Moderator Joined: 14 Feb 2004 Posts: 2048 Location: GBG