Mode 5 colour limitations?

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Nikku4211
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Re: Mode 5 colour limitations?

Post by Nikku4211 »

Dwedit wrote: Fri May 13, 2022 6:06 pm Meanwhile, In the vertical direction, interlacing will work its magic, and it will look double-resolution vertically.
That is if you can stand how interlacing looks on your TV, at least with a CRT. SNES doesn't natively have deflicker filters for interlacing either.
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kulor
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Re: Mode 5 colour limitations?

Post by kulor »

Dwedit wrote: Fri May 13, 2022 6:06 pm Old games used "Psuedo Hires" mode to do 50% transparency with another layer, so on a consumer television connected by Composite, it won't look very high-res. But it does work fine for white text against a dark background, Secret of Mana's hires text was quite readable.
This goes against what I've seen with my own testing though. I've tested on a number of sizes of consumer CRT TVs via composite, and mode 5 was noticeably more crisp on all of them.
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Re: Mode 5 colour limitations?

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kulor wrote: Fri May 13, 2022 11:35 pm This goes against what I've seen with my own testing though. I've tested on a number of sizes of consumer CRT TVs via composite, and mode 5 was noticeably more crisp on all of them.
Was pseudo-hires also more crisp? Did you see any vertical stripes when playing a SNES game like Kirby Dreamland 3 that uses pseudo-hires to fake more translucency?
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Re: Mode 5 colour limitations?

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Nikku4211 wrote: Sat May 14, 2022 11:05 am Was pseudo-hires also more crisp? Did you see any vertical stripes when playing a SNES game like Kirby Dreamland 3 that uses pseudo-hires to fake more translucency?
Pseudo-hires blends into transparency with a bit of a grainy texture. In mode 5, individual pixels are too fine to be discerned via composite on a CRT, and adjacent pixels do tend to blend together or have shifted colors. However, that doesn't mean the increase in resolution is imperceptible. To say "it won't look very high-res on a consumer television via composite" is inaccurate, at least from what I've seen.
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Re: Mode 5 colour limitations?

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In my tests, the hi-res luminance definitely comes through a bit on composite, but chrominance doesn't at all, as far as I can tell.

My feeling is that hi-res over composite is something like 1.5x the horizontal resolution for luminance only, maybe a little less. Even under blurring the "anti-aliasing" effect is still a benefit to the picture. The effect is very usable, though care should be taken not to rely on it to do more than it's capable of.

Interlacing doesn't have the bandwidth problem, so vertical resolution does more or less double, but it does introduce 30hz flickering that is more noticeable the more of this high resolution contrast you're trying to use. Also, when not interlacing it seems like some of the chroma artifacts end up cancelling each other out a bit on successive frames? (Not entirely sure, but the colour artifacts do seem to be worse in examples with interlacing.)

Also, I think it was already said earlier, but switching between interlaced and non-interlaced should be done sparingly, unless you want to annoy a lot of people with modern TVs, capture devices, and/or upscalers. On a lot of modern setups the picture will often drop a few seconds, or in some cases may require manual intervention to recover.

So in some ways, the extra detail trades for rainbow colour artifacts, though they're not necessarily very noticeable. In all cases it seems far less strong than what happens on NES. It might also help if the details are against a coloured but monochromatic field?

Examples:
  • In Syvalion, all of the thin white text as absolutely covered in rainbow errors. Probably a worst case example.
  • In Seiken Densetsu 3, the hi-res text has noticable diagonal fringing at all the edges. I think this might be mitigated a bit by the surrounding dark green field.
  • In Desert Fighter, wherever there is only 1 hi-res pixel gap between letters, they blur together (see: pre-mission screen). The coloured text of the mission overview seems to hide the chroma artifacts.
  • On RPM racing, the hi-res "noise" pattern in the road gives it some mild rainbow striping in a way that JP lo-res version doesn't seem to have at all. The title/logo/menu screens look pretty well, though, and don't seem to be suffering from hi-res, with the exception of some fine horizontal lines on the car bumper on the title screen which noticeably flicker under interlacing.
  • Jurassic Park pseudo-hires, depending on the TV this can look like a clean blend, or this can look very stripey.
The other day I took a few pictures of my CRT. They're not great photos, and there are some additional compromises, but I think they do illustrate the examples sufficiently:

syvalion.jpg
(480i) Syvalion shows a lot of colour errors on its thin text. Much of it is difficult to read. This screen is more or less verbatim copied from the arcade version, which would have had an RGB monitor instead of composite. Worst hit are the « » characters which due to their thin-ness and specific angle become entirely rainbow.

sd3_1.jpg
sd3_2.jpg
(240p) Seiken Denestsu 3 text comes through pretty well. There are noticable diagonal artifacts on all text, but for the most part it comes through pretty well. Many of the more complicated characters are borderline, though. Not using interlacing probably helps a lot, here. The green field might be helping suppress colour artifacts?

df_1.jpg
(240p) Desert Fighter's pre-mission screen has hi-res characters that have 2-pixel wide vertical strokes, but 1-pixel wide vertical gaps. The gaps tend to disappear entirely.

df_2.jpg
(480i) Desert Fighter's mission briefing has hi-res text. I think the choice of colouring mitigates the chroma errors. A lot of the detailed characters a significantly blurred.
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Re: Mode 5 colour limitations?

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rainwarrior wrote: Sat May 14, 2022 1:29 pm (Kanji examples)
Hmm, pretty interesting how a feature that sounds like it would be good for rendering such complex characters on paper ends up not too useful due to the video cables and TVs most people were using back then.

Then again, part of me thinks that the characters are just so complex that even in RGB on a 1-chip console, 16x16 or even 32x32 might not be enough to properly draw some of them.

I'm interested in seeing more examples of how Roman letters (and other alphabets like Cyrillic and Greek if you can find and run some fan translations) fare in higher-resolution modes on real hardware through a CRT with composite.
They don't really need the extra detail, of course, but it'd be interesting to see how something I should be able to read (like Latin letters) would become mangled.
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Re: Mode 5 colour limitations?

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rainwarrior wrote: Sat May 14, 2022 1:29 pm In my tests, the hi-res luminance definitely comes through a bit on composite, but chrominance doesn't at all, as far as I can tell.
Chrominance can't, in fact. NTSC composite is limited to somewhere around 140 pixels of chroma per scanline, so even just the 256px mode easily exceeds the permitted chroma bandwidth.

At least the 256px mode at least is guaranteed to display part of each pixel during both different phases of the chrominance subcarrier, so every pixel is guaranteed to contribute to the resulting color. This isn't true in the 512px mode, where a single pixel's color component can align exactly to the wrong phase and become invisible.

PAL changes things, but I haven't found a good discussion of how comb-filter PAL changes the effective bandwidth. (Without the comb filter, it's the exact same as NTSC without the aliasing problem mentioned above.) I suspect the effective bandwidth of PAL works out of half the subcarrier bandwidth, or maybe 210 pixels of chroma per scanline? The comb filter cleans up vertical edges, and only if two sequential progressive scanlines are the same color, but at some horizontal density the comb filter can't clean things up any more. You certainly still don't have anywhere near 512px of chroma, and I think still don't have 256px.
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Re: Mode 5 colour limitations?

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Nikku4211 wrote: Sat May 14, 2022 7:18 pmThen again, part of me thinks that the characters are just so complex that even in RGB on a 1-chip console, 16x16 or even 32x32 might not be enough to properly draw some of them.
I think all of these examples would probably look very clean on RGB (or S-Video).

The composite colour signal is the biggest problem here. There's a hard limit on how much detail you can encode, and various TVs will take stronger (blurrier) and weaker (error artifactier) approaches to decoding the signal.

Typical RGB computer monitors of the time should have had no problem with this resolution, if you could somehow connect an RGB SNES signal to them. I don't know much about consumer TVs with RGB from that era.... They might have their own filters that would reduce effective resolution, or have an unfocused picture, or other problems, but I think something truly built for RGB should easily be capable of having a nice clear picture?
Nikku4211 wrote: Sat May 14, 2022 7:18 pmI'm interested in seeing more examples of how Roman letters (and other alphabets like Cyrillic and Greek if you can find and run some fan translations) fare in higher-resolution modes on real hardware through a CRT with composite.
The US version of Desert Fighter, called Air Strike Patrol, has equivalent stuff in English, but since the characters are much simpler there is no deficiency of detail to speak of. I don't know if there's nearly as much value in trying to increase letter detail like this for English?

You can do half-width text that way, if you really want it. A.S.P. does this in that mission briefing screen, which probably does help them cram more text in, especially since English tends to be more "verbose" in terms of character count than Japanese. Important to note that the English characters in that example are mostly 6px wide with 2px gutters in between to keep them from running together.

I don't have a photo on hand, but I did test it and it looks entirely legible on my TV. It's less clear than regular width characters would have been, but still very readable. You can probably imagine based on this emulator screenshot:
asp.png
asp.png (9.58 KiB) Viewed 172 times

For a related example... Apple IIe has an 80-column mode, basically a 7x8 pixel grid at 560px horizontal resolution. On a monochrome monitor it's perfectly clear. On composite, it's a lot more compromised. If you set text mode it will disable the colourburst, and the 80 columns are legible but very blurry. If you render the same pixels but in graphical mode, which leaves the colourburst active, the text is illegible due to colour artifacts.

In theory my TV could probably render much cleaner 80-column text in text mode (colourburst off), but I don't think the TV is built to be able to disable the composite filter... so monochrome can remove the colour artifacts, but it still bandlimits the luminance and it can't make the text any sharper. A true monochrome TV on the other hand doesn't have that filter, and would display it very clean.

So... in general I tend to think that almost all of the problem is in the composite signal process.
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Re: Mode 5 colour limitations?

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rainwarrior wrote: Sat May 14, 2022 11:34 pm I think all of these examples would probably look very clean on RGB (or S-Video).

The composite colour signal is the biggest problem here. There's a hard limit on how much detail you can encode, and various TVs will take stronger (blurrier) and weaker (error artifactier) approaches to decoding the signal.

Typical RGB computer monitors of the time should have had no problem with this resolution, if you could somehow connect an RGB SNES signal to them. I don't know much about consumer TVs with RGB from that era.... They might have their own filters that would reduce effective resolution, or have an unfocused picture, or other problems, but I think something truly built for RGB should easily be capable of having a nice clear picture?
Oh I wasn't actually talking about these specific examples, I was just talking about CJK characters in general, I'm sure there are CJK characters out there where even a crystal clear 32x32 isn't enough to properly render them.
rainwarrior wrote: Sat May 14, 2022 11:34 pm For a related example... Apple IIe has an 80-column mode, basically a 7x8 pixel grid at 560px horizontal resolution. On a monochrome monitor it's perfectly clear. On composite, it's a lot more compromised. If you set text mode it will disable the colourburst, and the 80 columns are legible but very blurry. If you render the same pixels but in graphical mode, which leaves the colourburst active, the text is illegible due to colour artifacts.

In theory my TV could probably render much cleaner 80-column text in text mode (colourburst off), but I don't think the TV is built to be able to disable the composite filter... so monochrome can remove the colour artifacts, but it still bandlimits the luminance and it can't make the text any sharper. A true monochrome TV on the other hand doesn't have that filter, and would display it very clean.

So... in general I tend to think that almost all of the problem is in the composite signal process.
I actually wonder how much clearer hi-res would be in S-video on the SNES, since the colour and luminance are entirely separate signals in S-video, and CRTs that support S-video need to be able to tell the difference in order to benefit from the higher quality.
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Re: Mode 5 colour limitations?

Post by rainwarrior »

Nikku4211 wrote: Sun May 15, 2022 11:00 amI actually wonder how much clearer hi-res would be in S-video on the SNES, since the colour and luminance are entirely separate signals in S-video, and CRTs that support S-video need to be able to tell the difference in order to benefit from the higher quality.
I found these comparisons of SNES Composite vs S-Video vs RGB:
https://imgur.com/a/AyNF8
via
https://www.reddit.com/r/crtgaming/comm ... eo_vs_rgb/

Unfortunately hires examples aren't included there.

At the very least, S-Video eliminates inherent crosstalk between luma and chroma, so high resolution luminance doesn't have to bleed over as colour artifacts.

Depending on how the signal is generated, it might increase the bandwidth for luminance (less blurring, higher effective resolution), but chrominance would be the same. On the other end of the cable, it's up to the TV to utilize the separated signals well and bypass the usual composite separation filtering. So... at worst S-Video might look identical to composite, but at best there's a lot of clarity to gain.

The examples given don't have a lot of sharp colour contrast to demonstrate the difference between S-Video and RGB very well, because all of them show characters with black outlines in between mostly monochromatic regions of colour. One place you can see it is in the background behind Mega Man. The blue buildings with yellow vertical lines show up very clean in RGB and slightly fuzzy in S-Video, but it's pretty subtle.
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