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Screen Dimension Test program

 
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ccovell
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PostPosted: Fri Mar 09, 2007 5:13 pm    Post subject: Screen Dimension Test program Reply with quote

Hi, folks. I recently came across the PCE article on Wikipedia and came across this note about the PCE's resolution (a pet crusade of mine, if you'll remember.):
Wikipedia wrote:
Resolution:
X (Horizontal) Resolution: variable, maximum of 512 (programmable to 256, 352 or 512 pixels)
Y (Vertical) Resolution: variable, maximum of 242 (programmable in increments of 1 scanline)
The vast majority of TurboGrafx-16 games use 256224...

(I did not add the mention of my HiRes slideshow to Wikipedia, by the way. Wink )

I wondered, is this really true? So I tried out some games, and proceeded to make a little screen dimension test to see what the PCE could do on my TV and monitor. I'm sure others have made programs like this already, so if they have, please tell me.


http://www.disgruntleddesigner.com/chrisc/data/Screen_Dimension_Test.zip

I'll explain my findings [at length!] in using this program, and in testing out 277 PCE ROMs for their resolution and overscan settings:

Here are the maximum resolutions that I can get on my PC-Engine system and video monitor:

Low resolution (5Mhz clock): 282 x 242
Regs: $02,$00,$23,$0A,$00,$0E,$00F1,$03
Med. resolution (7Mhz clock): 377 x 242
Regs: $03,$02,$2F,$07 (rest are the same)
High resolution (10Mhz clock): 565 x 242
Regs: $00,$08,$46,$04 (rest are the same)

My TV (Panasonic, NTSC) has much less horizontal overscan visible (the usual 256 at the 5Mhz clock), but the full 242 lines are visible all the same.

Why did I make this?
--------------------
For a couple of reasons. The first is that a lot of PCE emulators don't display the full resolution and overscan borders that many games set the hardware to, and inside of which borders these same games display level and sprite graphics. This has been the source of some debate, with one side favouring clipping off the borders because "that part of the screen is not visible on my TV anyway", and the other side (me...) favouring displaying exactly what the game sets its screen attributes to, or at least as much as the PC-Engine is able to display of it.

The second reason is to determine the maximum resolution of the PC-Engine and various PCE games. The claims made on Wikipedia I found a bit suspicious.

So to put my money where my mouth is, I've tried out all the PC-Engine ROMs that I have and tested whether the majority set their (vertical) resolutions to something quite high, ie: near or past 240 lines; or low, around or less than 232 or 224 lines. Being as accurate as possible, then, I tested 277 licensed (meaning no Games Express), Japanese PCE ROMs, and noted their VDC settings.

28 (twenty-eight) of these games set their vertical resolutions to something around 224 lines.
249 (two hundred and forty-nine) games set their resolutions to around 240 lines.

I think it's fair to say that a vast majority of games (90%) use the higher vertical resolution. Wikipedia ought to have its entry corrected.

The most common VDC register setting in the 224-line camp was:
(from VSW:) $02,$17,$00DF,$04

Funny enough, the most common VDC register setting in the 240-line camp was:
(from VSW:) $02,$0F,$00EF,$04 (which actually sets up a 239-line screen.)

Yes, folks, when we put our demos into 240-line mode [using some reference values], we are actually limiting them to 239 lines. Here's a good setting for 240 lines, centred (meaning a blank scanline of sprite 0 palette colour visible on both the top and bottom):
(from VSW:) $02,$0D,$00EF,$04

And here's one for 242 lines (the maximum that I [and everyone else?] can get):
(from VSW:) $02,$0C,$00F1,$04

It had been mentioned that because some games display garbage in the top and bottom overscan areas, these areas should always be clipped in an emulator. Well in the course of my testing, I played each game to the in-game sections, and I only noted two games (of the entire 277) that had some unwanted junk or garbage in these areas. The first one I forget (sorry), but the other one was GranZort, which (at a generous 242 lines) shows some unwanted level graphics in the lower overscan area. Okay, that's two games out of almost three hundred, and we are clipping off valid graphics for all games just to accomodate these few? "Hmmmm....", I grumble.
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stevek666
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PostPosted: Sat Mar 10, 2007 12:47 am    Post subject: Reply with quote

Fascinating. I don't pretend to understand everything, but I would like a few things clarified:

1. I am not familiar with the "overscan" debate you referred to:

When you say that most (if not all) PCE emulators are clipping part of the display, what is your reference point? Is it the resolution that is declared in the code, or is it what a standard CRT television / monitor would display? Sorry for the newbie question, feel free to link to relevant sources so I can be educated Smile.


2. An overwhelming majority of your sample employs the 240+ vertical lines... but I'm curious about the horizontal resolution as well Smile. What is the most common resolution (X x Y), in your estimation?

Thanks in advance Smile
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ccovell
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PostPosted: Sun Mar 11, 2007 3:06 am    Post subject: Reply with quote

1. Yes, every PCE game has to define what its display parameters are. In other words, the programmers set the resolution of their games explicitly. I checked those 277 games to see what the majority of them did.

At the same time, I made the screen dimension test to see what my (and other people's) monitor and TV could display. Of course, this is only semi-relevant to the first item, since I think emus should follow the display parameters set by the game, within reasonable limits.

You can see the debate here: http://forums.magicengine.com/en/viewtopic.php?t=1580

2. Most games use a 256 pixel horizontal resolution. Some use more or less, of course. So based on my tests, the most common resolution is 256x239.

Update: I just did a test with my program on my TurboExpress, and from what I can make out, the maximum viewable area on the Express' screen is 261x238 in low-res mode; 518x238 in Hi-Res mode.
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Kaminari
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PostPosted: Sun Mar 11, 2007 6:59 pm    Post subject: Re: Screen Dimension Test program Reply with quote

ccovell wrote:
This has been the source of some debate, with one side favouring clipping off the borders because "that part of the screen is not visible on my TV anyway", and the other side (me...) favouring displaying exactly what the game sets its screen attributes to, or at least as much as the PC-Engine is able to display of it.


Honestly, I'm a bit tired of this :)

I don't know whether I'm supposed to be from the 'other side' or not, but anyway, forcing the border clipping for near-religious reasons is certainly not my philosophy. But let's elaborate once more.

Your Panasonic displays the full vertical overscan, that's great. My Commodore 1084S can do it as well, but I have to change the factory settings for that and and I don't consider it a standard procedure. Out of the dozen of regular TVs I tested over here, none of them displays more than 224 lines (minus two or three lines that are barely visible on non-flat tubes). And no game I can think of is missing any vital gameplay information past the 224 lines. Last but not least, out of all the PCE games I played in my life, most of them clearly look like they were designed with the 224 lines in mind (think about how the graphic elements like background tiles, status bars, menus, inventory frames, etc. often fit the 256x224 area).

Conclusion: games were designed to use 224 lines for practical reasons, but developers would usually let the system draw in the overscan zone because, as we all agree, the system can do it. This is no news. Truckloads of Amiga games have done this. If you tweak your monitor/TV, you can see a lot of added surface, and that's hip, but nothing that was meant to be essential for gameplay (for obvious reasons).

Don't take it personal Chris, but there's no crusade. There's nobody that disagrees with you about what the system can display. There's no '224 line conspiration'. It's just that Magic Engine currently simulates what most TVs can actually display, and that's 224 lines. But in the near future, people will be able to set the maximum visible resolution in ME to what they see fit, as it's already possible in MEFX (only for horizontal resolutions right now). I don't know about the other emulators, but as far as ME is concerned, the 'problem' will soon be solved.

As a sidenote, and as much as I like ME, I consider Ootake to be a project that aims for extreme accuracy. I think there's a reason why it's limited to 224 lines as well, but I'll be interested in hearing what Kitao Nakamura has to say about it.
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stevek666
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PostPosted: Mon Mar 12, 2007 1:47 am    Post subject: Reply with quote

Chris, thanks for the info Smile. I finally "get it" now.

I have another follow-up question: Do CD / SCD games differ significantly from HuCard games as far as screen resolution is concerned?

If I were to hazard a guess, I'd suspect that different resolutions might be used during cinemas / special effects .... but that actual gameplay in CD games would share the same constraints of the HuCard games (again, as far as resolution is concerned).

Is this a reasonable assumption? Thanks in advance Smile.
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ccovell
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PostPosted: Mon Mar 12, 2007 3:38 am    Post subject: Re: Screen Dimension Test program Reply with quote

Stevek: I haven't gone and tested any CD games, but I don't think there is a significant difference. A game usually doesn't change resolutions between game and cinemas (though R-Type complete springs to mind). If you have some good examples of games that do, please post them.

Kaminari wrote:
I don't know whether I'm supposed to be from the 'other side' or not, but anyway, forcing the border clipping for near-religious reasons is certainly not my philosophy. But let's elaborate once more.

Heh, I used the "crusade" word in a joking way. I don't take it personally (not at all, this debate is interesting and is good fuel for my brain), but I guess the scientist/anal retentive in me can't sit idly by and read things like 224 lines being "accurate" in most senses of the word. Read below.

Kaminari wrote:
Your Panasonic displays the full vertical overscan, that's great...

...and all our TurboExpresses/PCE GTs.

Kaminari wrote:
...out of all the PCE games I played in my life, most of them clearly look like they were designed with the 224 lines in mind...
...games were designed to use 224 lines for practical reasons, but developers would usually let the system draw in the overscan zone

Thank you, you have just proven my point. My point all along was this: Yes, most games display only 224 lines of worthwhile graphics, but there are games that were designed and drawn to display more. On the one hand, if we display the full 240 lines of a game whose graphics are only designed for 224 lines, there's no loss, since "developers would usually let the system draw in the overscan zone". Displaying all the scanlines set by the game, even when not all are being used up by graphics, is not visually distracting. Can we at least agree on this?

On the other hand, if we take games that have graphics designed and drawn across 240 or 242 lines and then through emulation limit their display to 224 lines, something is being lost. Graphics in games and in cutscenes are being masked to an extent. Surely you must agree here too.

Kaminari wrote:
As a sidenote, and as much as I like ME, I consider Ootake to be a project that aims for extreme accuracy

I think your idea of what "accuracy" means, then, is different from mine.

The NTSC standard provides for 262/263 scanlines. The PCE outputs 242 lines of valid graphics. The Turbo Express displays 238 lines on its screen. If one wanted accuracy he/she would stick to one of these three settings.

David (and other emu authors) is setting his resolution to something, not accurate, but familiar. Of course, I can understand that. But it has prompted me to seek out more accurate PCE emulators when I needed accurate screenshots of games (for example when making maps for Neutopia, and other reasons.)

Anyway, that's all I have to say this time. Smile
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nodtveidt
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PostPosted: Sun Mar 18, 2007 6:03 am    Post subject: Reply with quote

Somewhat on-topic: A long time ago, I had started a project to bring Neutopia to the GBA. I started by attempting to map out the first sphere by hand, using Magic Engine. I got a little frustrated because each screenshot clipped the lower part of the tiles and I couldn't get an accurate map. I figured that that's the way it was, but knowing that it wasn't that way...well, it's interesting

Although I abandoned the project...the GBA's resolution is too low to handle a pixel-per-pixel port.
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