
Transparency effects in SNES and Genesis games via composite video artifacts - kibwen
https://nerdlypleasures.blogspot.com/2015/03/the-case-for-composite.html
======
byuu
I'm sorry to be the bad guy here and point this out, but ... this article is
completely wrong :/

An emulator outputting 100% perfect RGB pixels onto an LCD screen is very
different than running an analog RGB output to a CRT television.

I have a PVM-2530 CRT, and a hand-built Multi-AV to PVM-CMPTR adapter board (
[http://i.imgur.com/EgCX2EJ.jpg](http://i.imgur.com/EgCX2EJ.jpg) ), and the
colors still blend perfectly fine in his example of Kirby's Dream Land 3, as
well as the more odious test case of Jurassic Park's translucent menus.

CRTs don't have an "official" horizontal resolution .. the number of RGB
columns is dependent upon the tube and its size, and there's never an exact
match against the analog nature of the RGB output from the SNES to the columns
on a TV. So the colors naturally bleed together and produce the desired
translucency. Maybe just a touch less severely than composite, but well more
than enough to achieve the desired blending effects -- without all the
horrific composite video artifacts.

Further, my SNES emulator simulates this effect as well, by choosing "Video
Emulation -> Blurring." It doesn't quite work the same way as a CRT would, but
it simulates the effect very nicely. It's not yet connected for my Genesis
emulator, but that's only because it's very new and has more pressing issues
to address, but it'll be there in time as well.

I can't speak for how these effects look on an XRGB-Mini (I haven't tested
these types of translucency tricks on mine yet), but I would venture a guess
that it would not even look close to as 'pristine' (striped) as the emulators
output: it's still having to use an ADC on the RGB lines, and that's always
going to be lossy to some degree.

~~~
boomlinde
_> An emulator outputting 100% perfect RGB pixels onto an LCD screen is very
different than running an analog RGB output to a CRT television._

I don't see the article suggesting otherwise. It suggests that some of the
artefacts inherent to composite video encoding are not present in RGB.

I agree that the effect varies depending on the tube and the device, but in
general I've found the blurring to be more pronounced in composite encoding,
not to mention having a distinct quality.

Here are actual frame captures compared:
[http://www.chrismcovell.com/gotRGB/rgb_compare2.html](http://www.chrismcovell.com/gotRGB/rgb_compare2.html)

~~~
drewmate
It looks like a lot of those effects are possible because when outputting to
composite, the horizontal rows are well-defined, while the vertical columns
are not and unlikely to precisely match/map the output. For instance, there
are a lot of clean gradients from top to bottom (clean rows of color) which
use dithering in the rgb output. Columnar gradients would have bleeding/blurry
edges due to the unpredictable nature of the analog display. Am I
understanding this correctly?

------
mrob
This did not happen with all displays. I used an original Playstation with a
Commodore 1084S monitor [1] connected via RGB with custom connector I built,
using a LM1881 [2] to split the composite sync signal for the RGB mode's
separate vertical and horizontal sync. This had excellent sharpness and
dithering was always clearly visible. Both the Genesis and the SNES (non-mini
versions) output RGB without modification and can be used with that same
hardware.

In any case, it's unlikely that blurring was always intended. The article
shows a screenshot from Chrono Trigger where a dithering-style checkerboard
pattern is instead used to represent the keys of a typewriter. It would be
difficult to tell what it was supposed to be if there was enough blur to hide
dithering. Official artwork from NES-era Nintendo often showed characters
drawn in a sharply pixelated style. And portable systems used LCD displays
with no blurring, but dithering was still used extensively.

[1]
[https://www.c64-wiki.com/wiki/Commodore_1084](https://www.c64-wiki.com/wiki/Commodore_1084)

[2]
[http://www.ti.com/lit/ds/symlink/lm1881.pdf](http://www.ti.com/lit/ds/symlink/lm1881.pdf)

~~~
laumars
On CRTs the pixels on PC monitors were arranged differently to TVs, which is
why your Commodore screen was sharper than the typical console hook up.

From what I recall (it's been a long, _long_ , time since I've studied this)
PC monitors were a typical square grid layout, much like how LCDs are. Where
as TVs had the odd and even lines offset by half a pixel - a bit like a
hexagon grid.

~~~
mrob
Aperture grille CRTs had that layout, but the 1084 was just a regular shadow
mask CRT.

------
Torgo
In Europe and Japan a lot of TVs just had SCART with RGB pins so I don't think
it was too unusual for people to have setups like this at the time. Not
discounting what the author is saying, but I have to assume that designers
planned for a lot of people using RGB or at least decided what their tradeoffs
were going to be.

~~~
jacobush
Also arcade games were very often RGB, so games with artwork from arcade games
could have been designed for RGB.

But I have to say, I don't think "designers" back then thought much about
hardware setups different from their own!

It was different times and stuff had to ship fast, fast fast.

------
Agustus
The ability of a programmer to take advantage of an effect specifically found
only on a quirk in hardware is an art skill that may be going the way of the
dodo bird. Not having to port a game between varying resolutions like this
article mentions means you can play visual tricks. The article demonstrates
the curtain being revealed in the last comparison of Kirby games.

------
rocky1138
This is very similar to how CGA worked on the IBM PC.

[https://www.youtube.com/watch?v=niKblgZupOc](https://www.youtube.com/watch?v=niKblgZupOc)

~~~
Zardoz84
Don't forget Apple ][ . Wozniac abused of NTSC artifacts to generate colors.

------
emptybits
When "perfect" emulation (or pixel-perfect "better" displays) fall short of
the _real_ goal. Art. :-)

------
floatboth
I like the sharpness of RGB though, composite looks a bit blurry. As someone
who grew up with emulators and ports (J2ME, Nokia N-Gage…) I'm used to e.g.
the vertical stripes on water in Sonic :D

------
Malic
Somewhat related to those that would like to know more...

Great efforts were made to extend the Atari 2600 emulator, Stella, to deal
with the imperfections of CRT displays that games of yesteryear depended on.
Ian Bogost, co-author of "Racing the Beam"
([https://mitpress.mit.edu/books/racing-
beam](https://mitpress.mit.edu/books/racing-beam)), lead a team to make a code
contribution to Stella that attempted to emulate the visual qualities that
CRTs exhibited.

"...In Spring 2009, I tasked a Georgia Tech Computer Science capstone group to
modify Stella, adding settings to simulate the CRT behaviors described above.
The group consisted of five committed and talented CS seniors: Edward Booth,
Michael Cook, Justin Dobbs, Will Rowland, and Prince Yang..."

[http://bogost.com/games/a_television_simulator/](http://bogost.com/games/a_television_simulator/)

------
starquake
Raspberry PI can do 240p over composite now:
[https://github.com/raspberrypi/firmware/issues/683](https://github.com/raspberrypi/firmware/issues/683)

The reasons portrayed in the article are exactly why I prefer this setup over
RGB.

~~~
jacobush
Yay! I have been waiting for this.

------
zellyn
FYI, there's currently a fairly interesting related discussion going on under
my comment on the "disappearing CRTs" article:
[https://news.ycombinator.com/item?id=13802917](https://news.ycombinator.com/item?id=13802917)

------
alexyoung
I prefer the crisp output of RGB because it's how the better arcades looked to
me in the late 80s and early 90s. High quality upscaling with scanline
emulation is about as close as that as I can get at home.

------
smilekzs
TL;DR anti-aliasing filter and dithering

------
Dirlewanger
I think there are a few modern games out there that emulate this effect.

------
bluedino
Does the 'blurred' version give anyone else a headache?

------
draw_down
I dunno... look at the checkerboard-pattern background in the first set of
screenshots from Sonic. (The one "behind" the falling water.) Why is that
blurrier in the "RGB" version? That's just a pattern of squares, I'm not sure
composite video artifacts or whatever are the reason the "RGB" one looks so
blurry.

~~~
crooked-v
> Why is that blurrier in the "RGB" version?

You're asking the wrong question. It's _not_ blurrier in the RGB version. The
point is that the graphics were designed for a blurry display method, so by
not being blurry, the RGB version has a worse result.

~~~
draw_down
It is blurrier!

~~~
kalleboo
Everything looks pixel perfect to me in the RGB screenshots (the first one in
each set). Is there something wrong with your monitor?

