Modifying colours on MSX1...?

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By RSS

Rookie (17)

RSS's picture

02-05-2014, 18:01

Hmmm. When I do that VDP(0)=VDP(i)or1 on my Philips VG8020 then all I get is monochrome gray.
Weird!

By hit9918

Prophet (2927)

hit9918's picture

03-05-2014, 22:42

I feel like I got some news Smile MSX1 = composite! Except for rare exotics, the only thing is composite.
a scart connector has no meaning, it has a composite pin.

@RSS, I wasn't about a code but about pixeling for composite.
Type color 6,7 and see.
The letters get messy. While the cursor looks like a tile with highlight and shadow.
On its left side is color 6 in the brightness of color 7,
on the right side is color 7 in the brightness of color 6.
Like automatic highlighting of a mono sprite Smile
Other colors have same principle, with varying amount of noise.
To minimize noise, the sprite should be a shape like the cursor, closed horizontal lines without sky color shine thru.

By hit9918

Prophet (2927)

hit9918's picture

10-05-2014, 12:13

LOL! Algorithm for composite video emulation. This is the result:

this is a capture of the real machine:

this was the screen 2 pic in vram:

Unbelievable, just look at the NES tile :D and it is even scrollable.
The capture is a messy TV stick via antenna cable, on flatpanel TV it looks great.
It needs no code, but I feel like looking at a new MSX1 screen mode :D

Please could this be put into openmsx?
The viewer and source code is at
https://sites.google.com/site/tueftlerlabs/home/downloads/composite_viewer.zip?attredirects=0&d=1

By ARTRAG

Enlighted (6933)

ARTRAG's picture

10-05-2014, 13:17

Imho it will depend too much on the display and its connectos to be used realiably

By hit9918

Prophet (2927)

hit9918's picture

10-05-2014, 14:06

maybe the principle holds?
some things aren't pixel exact anyways, only question is whether games look better.

anyone who has his real machine handy, turning it on and saying color 6,7 and looking at the cursor is all it takes to see. we could need statistics how many displays do the same.

By sd_snatcher

Prophet (3647)

sd_snatcher's picture

10-05-2014, 15:44

@hit9918

Ok, got it, and I agree with you.

To help you with your quest, I add that what you're trying to say is exactly the idea explained here and with even more detail here.

s-video is the best compromise in this aspect. It does the chroma interpolation that mix the colors and create new hues as you want, without introducing the horrible jaggies and lack of focus that composite have.

And yes, as Blargg mentions, it seems that the Japanese artists of the 80's games created the graphics taking the chroma interpolation effect into consideration. The V9958 YJK system was the same idea, implemented in hardware.

But the effect is intimately tied to the color system used. So we're talking about NTSC here (YIQ colorspace), and not PAL (YUV colorspace).

By sd_snatcher

Prophet (3647)

sd_snatcher's picture

10-05-2014, 15:52

Forgot to mention: many MSX2 (screen5) games clearly used this technique. Apply the NTSC chroma interpolation filter over the YS2 or Valis2 graphics and check the results yourself. Smile

By hit9918

Prophet (2927)

hit9918's picture

10-05-2014, 21:44

I rewrote it to real YUV
https://sites.google.com/site/tueftlerlabs/home/downloads/composite_viewer.zip?attredirects=0&d=1

It softens the red hat jaggies of the other thread. The model isn't really mixcolor but "change color one pixel ahead while keeping brightness". Very different to what a blur on rgb values makes.

Look at this ntsc capture:
http://www.youtube.com/watch?v=ZuY9RxIC57E&t=0m35s
It too has a "change color one pixel ahead" look.

By Grauw

Ascended (10722)

Grauw's picture

10-05-2014, 23:53

I ran my avatar (from Ys 2) through the viewer… didn’t think it looked better, just blurrier with colour bleeding Smile.

By sd_snatcher

Prophet (3647)

sd_snatcher's picture

11-05-2014, 00:15

@Grauw

In this case, like other enhancement filters (2xSai, Scale2x) personal taste also influence a lot on the perception of the result. A lot of people dislike the results of 2xSai or Scale2x because they fell that the image got blurred or lost detail.

Can you post the resulting image, along with one screenshot from the first underground area of the game? Try to take the screenshot next to the area that two rocky enemies guarding a chest. That area has trees, sand and a lot of different tiles if I recall correctly.

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