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PostPosted: Sun Apr 30, 2017 8:54 am 
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(Not sure if this is the correct forum; as it concerns the NES, Super NES, and Mega Drive, I couldn't think of anywhere else that doesn't put a bias towards any single console.)

There's something I've been wondering about whenever anyone mentions what aspect ratio they prefer. And this is going to sound pedantic. And maybe someone posted about it before already.

Some people will say that they prefer 4:3 aspect ratio for the NES and Super NES. But is that really accurate?

The pixel aspect ratio of both consoles is 8:7. If one applies this pixel aspect ratio to a 256×240 image, the result would translate to (2048/7)×240 (approximately 292.57×240) on a display that only supports square pixels. But that's not 4:3. With a height of 240 scanlines, the width would need to be 320, not 2048/7 (292.57). In actuality, the display aspect ratio would be 128:105 (3.28125:3), not 4:3. Note that this is not counting the border regions to the left and right of the NES's visible region where the background color is displayed.

I don't think I've seen "128:105" mentioned anywhere on the NesDev wiki. But that is the display aspect ratio used when the pixel aspect ratio is 8:7 and the borders are excluded.

The Mega Drive also has the same pixel aspect ratio when using 256px mode, and in 320px mode, its pixel aspect ratio is instead 32:35. With a height of 224px, its display aspect ratio is 64:49 regardless of whether its horizontal resolution is 256px or 320px. Even if one counts the blank scanlines at the top and bottom, the display aspect ratio will still be 128:105 instead of 4:3.

I don't have an NES Classic Edition, but I suspect that Nintendo may also be guilty of this same misconception (using 4:3 instead of 128:105). In its internal files is an image that is used to represent the CRT Filter option. It is titled "capture_analog.png", though it isn't actually a file all to itself; it is part of a larger composite image that contains all the graphics in use. That being the case, its exact dimensions are 240×180, which is a 4:3 display aspect ratio.

So when people request a 4:3 display, they are actually getting a display that is even wider than what the actual consoles output. In order to stretch a display this far, the pixel aspect ratio would need to be 5:4, not 8:7 (1:1 in the case of the Mega Drive at 320px). Is this actually desirable to some people? Does it actually look better at 4:3 instead of 128:105? Or are they actually referring to 128:105 with some all-black padding to make it 4:3?

Here is an example with perfectly square pixels: (PAR: 1:1, DAR: 16:15)
[spoiler]Image[/spoiler]

Here is an example of what a 4:3 display would actually look like: (PAR: 5:4, DAR: 4:3)
[spoiler]Image[/spoiler]

And here is an example that is closer to what the consoles actually output: (PAR: 8:7, DAR: 128:105)
[spoiler]Image[/spoiler]


Last edited by hex_usr on Sun Apr 30, 2017 9:33 am, edited 1 time in total.

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PostPosted: Sun Apr 30, 2017 9:29 am 
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Quote:
With a height of 224px, its display aspect ratio is 64:49 regardless of whether its horizontal resolution is 256px or 320px.

And this is very close to 4:3.

Technically, the "4:3" display aspect ratio refers to the entire 350x240 pixels (Genesis in 40-cell mode) or 280x240 pixels (other ColecoVision derivatives), including borders, that are within the clean aperture (52.148 µs by 240 lines) specified by Rec. 601. But people remember the display with the overscan chopped off. Emulators tend to approximate the visible image as 256x224 or 320x224 pixels, which is 64:49 DAR, and 64:49 is close to the nominal 4:3, just as "2.35:1" is close to the actual ratio of scope, which is 2.39:1 on film or 2.40:1 on Blu-ray. And when upscaling for HDTV, you usually want to display it as if the overscan were also upscaled, as HDTV programming on broadcast and cable is generally formatted with overscan to accommodate early-adopter CRT HDTVs. This means upscale the entire 280x240 or 350x240 pixels to 960x720 or 1440x1080.


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PostPosted: Sun Apr 30, 2017 9:51 am 
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tepples wrote:
And this is very close to 4:3.

Thanks, I didn't pick up on that at first. That would also apply to the Super NES when it renders 224 scanlines instead of 239.

I just checked Mesen, and it crops the top and bottom 8 pixels by default, which I think puNES does not do by default. And I usually disable overscan cropping anyway, so I forgot that it could be a default in some emulators.

It was this post that inspired my question. That, and a suspicion that Nintendo made the exact mistake I described above in the NES Classic Edition (I would love to be proven wrong by someone who has one, though).

Let's see: if the borders are counted, making a 280×240 display, and it has square pixels, its display aspect ratio would be 7:6. But I don't think I ever saw anyone actually mention "7:6" when stating that they want a 4:3 display, which probably added to my motivation to make this thread.


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PostPosted: Sun Apr 30, 2017 10:54 am 
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Location: NE Indiana, USA (NTSC)
Many TVs of the time placed the picture slightly above center, cutting off more on the top than the bottom. I speculate that this has something to do with the NES and Super NES frame rate being 60.10 Hz, which is slightly faster than the 59.94 Hz of the NTSC standard. (The Genesis frame rate is 59.92 Hz, showing less of this problem.)
Attachment:
File comment: Nominal overscan of 4.4%
4.4_overscan.png
4.4_overscan.png [ 6.79 KiB | Viewed 355 times ]


In fact, Nintendo's original "Background Planning Sheets", as seen in features on the making of Super Mario Bros. and The Legend of Zelda, encouraged keeping critical text 16 pixels from the sides and 24 from the top and bottom. This meant that only 80 percent of the width and height of the 280x240 pixel plane was usable. I imagine that this improved compatibility with older TVs from the 1970s.
Attachment:
File comment: Worst case overscan of 10%
10.0_overscan.png
10.0_overscan.png [ 6.88 KiB | Viewed 355 times ]


I've tried to standardize names for the various "safe areas", or estimates of the area not cropped by overscan, on 5.37 MHz NTSC VDPs like those in the NES, Master System, Genesis, and Super NES.

Image
Danger zone, action safe, PocketNES safe, and title safe areas


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PostPosted: Sun Apr 30, 2017 12:14 pm 
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Ooh! Ooh! I get to use this image again!
Attachment:
smb1_tv_crop.png
smb1_tv_crop.png [ 3.88 KiB | Viewed 333 times ]

How my 1981 TV crops Super Mario Bros.

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PostPosted: Sun Apr 30, 2017 1:47 pm 
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about tepples and Nintendo planning sheets: the reason you mentioned for the safe area recommendation is probably correct, and it reminds me of what I read in an interview about how the guys from Epoch would actually go to your house and adjust the pots on your TV set if needed if you bought their pre-Cassette Vision pong consoles.

Quote:
In a way, though, I was lucky. I wasn’t told this during the interview, but they were actually right in the middle of developing the System 10. It was released in 78, and I helped with the sales then too. The thing is, you see, no one had ever connected a video game to their TV before, or knew exactly how that would work: not Epoch, not our customers, not the industry. Today we have video inputs but before that you had to use the switchbox and turn to channel 2, where the signal would be broadcast wirelessly. We all know that’s how it works today, but at the time we were gripped with anxiety on a daily basis: what if consumers turn it on, and nothing shows up on-screen…?

In an era before the Famicom, therefore, I was actually breaking new ground in my job. We ran an amazing info campaign to help people understand how these new games worked. I was working out of the Osaka sales office then, but if a customer was having problems, we’d almost always go to their home directly. It was too difficult to explain how to fix it over the phone. We worked in the area from Osaka to Wakayama. There’s so many nice people in Kansai. Talking to them on the phone I’d sometimes feel a little scared, but the people I visited were very kind. They would even treat me with beer and dinner sometimes!

Old television screens were smaller than they are now and the corners were rounded off, so lots of times the entire game wouldn’t fit on screen. I often had to open up the TV and adjust the horizontal and vertical pots. I’d have to get back behind the TV, use a vacuum to get all the dust off, make my adjustments and then move everything back in place. Nowadays we’d call it an occupational hazard. (laughs)

That Osaka sales job was the best place to learn those technical things, though. I had to write a lot of reports!


Placing critical information in a place where TV sets would only clip them off if it was very poorly adjusted was probably an intelligent way of reducing user support costs :P

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