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NTSC pattern torture test ROM
http://forums.nesdev.com/viewtopic.php?f=2&t=15080
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Author:  Sour [ Fri Dec 30, 2016 5:26 pm ]
Post subject:  Re: NTSC pattern torture test ROM

Zepper wrote:
Does not work here.
Are you trying to run Eugene's build?
It's probably dynamically linked against MSVC's standard library. "Official" builds are statically linked, so that shouldn't happen.
You can grab Mesen 0.7.0, it has the filter & should work.
Otherwise, you can also install the VC++ 2015 x86/x64 runtime on your PC and it should fix the problem, too.

Author:  Zepper [ Fri Dec 30, 2016 6:04 pm ]
Post subject:  Re: NTSC pattern torture test ROM

Got the official version, worked fine. Btw, blargg's NTSC version looks better.

Author:  dougeff [ Mon Feb 13, 2017 9:27 pm ]
Post subject:  Re: NTSC pattern torture test ROM

I did some tests of my own on an NTSC TV with some dither patterns...kind of interesting, I think.

Attachment:
DitherB.jpg
DitherB.jpg [ 566.5 KiB | Viewed 1016 times ]


Original, much larger picture...

http://dl.dropboxusercontent.com/s/y0ty ... Dither.jpg

Author:  tokumaru [ Mon Feb 13, 2017 9:49 pm ]
Post subject:  Re: NTSC pattern torture test ROM

dougeff wrote:
I did some tests of my own on an NTSC TV with some dither patterns...kind of interesting, I think.

It would be interesting if you posted the pixel-perfect image for comparison.

Quote:
http://dl.dropboxusercontent.com/s/y0tyq4w45hdv1ak/Dither.jpg

Today's lesson: Don't ever use dither patterms on the NES. :wink:

In all seriousness, I guess there are a few legitimate reasons to use dithering, but the basic notion that you can create uniform colors definitely doesn't apply here, specially if the image is supposed to scroll. The only time I absolutely needed to use dithering was on my raycaster, but the big software pixels and lack of scrolling really helped.

Author:  Revenant [ Mon Feb 13, 2017 11:05 pm ]
Post subject:  Re: NTSC pattern torture test ROM

dougeff wrote:
http://dl.dropboxusercontent.com/s/y0tyq4w45hdv1ak/Dither.jpg


Ooh, carpet tiles.

Author:  dougeff [ Tue Feb 14, 2017 6:36 am ]
Post subject:  Re: NTSC pattern torture test ROM

This is what it looks like in FCEUX...

Attachment:
dither.png
dither.png [ 2.51 KiB | Viewed 969 times ]


Here is the ROM. I added scroll left and right function. You can see it pretty good in Nestopia with the NTSC filter on. (didn't test any others)

Attachment:
dither.nes [24.02 KiB]
Downloaded 30 times


I think the clear winner is the horizontal striped bars. They don't change or flicker or get weird diagonal patterns when scrolling. (in the picture, not the top left, but just to the right of that).

Further investigation...
I did some tests with very similar colors, and I find that dithering with a slightly lighter shade of the exact same hue (15 with 25) produces smoother look, even on NTSC. Still getting diagonal lines on most of the patterns though.

Author:  tokumaru [ Tue Feb 14, 2017 8:41 am ]
Post subject:  Re: NTSC pattern torture test ROM

Interesting how the worst offender (i.e. the one that results in diagonals with the highest contrast) is the basic checkerboard pattern that many inexperienced artists would try.

Author:  feos [ Wed Feb 15, 2017 8:09 am ]
Post subject:  Re: NTSC pattern torture test ROM

dougeff wrote:
I did some tests with very similar colors, and I find that dithering with a slightly lighter shade of the exact same hue (15 with 25) produces smoother look, even on NTSC. Still getting diagonal lines on most of the patterns though.

Pictures?

Author:  dougeff [ Wed Feb 15, 2017 10:40 am ]
Post subject:  Re: NTSC pattern torture test ROM

Here's a picture. NTSC CRT TV. Colors 15 25, 1a 2a, 11 21, 05 15

I'm going to try to make a video.

Attachment:
dither2.jpg
dither2.jpg [ 309.04 KiB | Viewed 889 times ]


Attachment:
dither2.png
dither2.png [ 2.52 KiB | Viewed 880 times ]

Author:  feos [ Wed Feb 15, 2017 10:48 am ]
Post subject:  Re: NTSC pattern torture test ROM

Right, and the source (aka plain emulator output)?

Author:  tepples [ Wed Feb 15, 2017 10:52 am ]
Post subject:  Re: NTSC pattern torture test ROM

Stripes in dither patterns are caused by chroma spilling over into frequencies associated with luma (0-3.0 MHz). This happens when the signal is high or low for significantly longer or shorter than half a cycle of the color subcarrier, particularly when switching between different hues. But when the hue is the same (e.g. $15 vs. $25), that just changes the luma level, and the TV successfully separates out the changes in luma from the (lack of) changes in chroma. You see some faint stripes in the checkerboard pattern with $05 and $15 (row 7, column 3) because the chroma is stronger (more saturation) in $15 and $25 than in $05 and $35.

feos: In each case, the plain emulator output resembles the white portion of the original attachment.

Author:  dougeff [ Wed Feb 15, 2017 10:58 am ]
Post subject:  Re: NTSC pattern torture test ROM

Video

https://youtu.be/bD7mNw5McBs

Also, edited above post to include 'emulator output'.

I probably need to adjust mt TV's color. $15 is coming out purple.

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