Dreamcast Dithering?

guyjin · 01/09/2010, 12:35 AM

So I got my (unofficial) Dreamcast VGA adapter today. Unfortunately, there seems to be a problem.

I see dithering.

I know that this is impossible, since the Dreamcast should have plenty of colors to display without having to resort to that, but it exists:

that was the best picture I could get of it from my HDTV. it always seems to follow geometric patterns, like checkerboards or dots in perfect rows and columns.

Anyway, I've messed with every setting I know how to mess with, and nothing helps. WTF is going on?

ccovell · 01/09/2010, 01:03 AM

The N64 and Playstation 1 (and others?) also dither their graphics in the same way. Perhaps someone with more technical knowledge could explain why. Anyway, it's not a bug or problem with your VGA adaptor; it's a "feature" of the system.

Joe Redifer · 01/09/2010, 01:23 AM

What game is that? If I have the same game I will check to see if it does it on mine.

Tatsujin · 01/09/2010, 03:03 AM

yeah, it's a feature!

i tought that lot of 2D games of later system using kind of compression which then looks like dithered. e.g. SNK BeU like last blade etc. on the PS and also DC.

SignOfZeta · 01/09/2010, 03:21 AM

This might be related to the game, so what game is that? It looks 2D, and that brings with it a high probability of there just being a problem with the bitmaps (or whatever) that are in the game. Honestly the roughness of that black line looks pretty jpegy. A LOT of 2D games suffer from all sorts of problems with compression, fake low res, conversion, etc. I'll check too, if I have the game. I don't use LCD TVs, but I have a monitor I can check it with.

There is (almost) certainly no problem with the VGA box since the DC puts out VGA natively, but the signal is 640x480. Is your "HDTV" an LCD? If so, can you display the image not scaled in any way? If it is being stretched to fill the horizontal height then this could also be an artifact inherent to the scaling hardware of your TV.

ParanoiaDragon · 01/09/2010, 04:24 AM

It's clearly a game with Mickey Mouse in it! Seriously, that's the first thing that comes to mind........am I right or am I right or am I right,.... I'm right, right? I'm probably wrong, but whatever, I STILL say it's Mickey anyways

Arkhan Asylum · 01/09/2010, 06:02 AM

it looks like either samba de amigo or power stone to me.

esteban · 01/09/2010, 09:39 AM

Screenshot detail is from Soulcalibur, ending credits.

Tatsujin · 01/09/2010, 09:48 AM

it's a huge mushroom!

guyjin · 01/09/2010, 11:06 AM

hahaha, I need to start a Dreamcast screenshot quiz!

it's actually from Crazy Taxi 2. it's the intro logo.

but back to the issue, yeah, I have the TV set to "aspect" (stretches the screen but not out of proportion). I'll try again with it set to 1:1.

edit: setting it to 1:1 seems to work, but it's so small I'm not sure.

Joe Redifer · 01/09/2010, 07:05 PM

ANY stretching makes the picture out of proportion.

EDIT: I don't seem to have either Crazy Taxi game, not even on CD-R. I have a Crazy Taxi 2 save file, though. I remember the game becoming boring after a couple of hours so maybe I sold it. Do any other games boot up with the same logo? I am not seeing any dithering on my TV and I have my Dreamcast connected with a VGA box that coes to a VGA-Component transcoder so I can play the games in 480p.

SignOfZeta · 01/09/2010, 10:55 PM

Quote from: Joe Redifer on 01/09/2010, 07:05 PMANY stretching makes the picture out of proportion.

In theory if you had a screen with exactly four times as many pixels, 1280x960, you could exactly double the size of the image without distortion.

In practical use though, yeah, its always going to fuck it up. Furthermore, the best way to play DC games is on a VGA CRT.

guyjin · 01/10/2010, 02:08 AM

Quote from: Joe Redifer on 01/09/2010, 07:05 PMANY stretching makes the picture out of proportion.

oops

QuoteI am not seeing any dithering on my TV and I have my Dreamcast connected with a VGA box that coes to a VGA-Component transcoder so I can play the games in 480p.

What is that, where might I find one, and is it worth it?

SignOfZeta · 01/10/2010, 02:29 AM

Quote from: guyjin on 01/10/2010, 02:08 AM
Quote from: Joe Redifer on 01/09/2010, 07:05 PMI am not seeing any dithering on my TV and I have my Dreamcast connected with a VGA box that coes to a VGA-Component transcoder so I can play the games in 480p.
What is that, where might I find one, and is it worth it?

I don't see how it could be unless your TV didn't have a VGA port. The DC VGA output is 480p.

SNKNostalgia · 01/13/2010, 03:00 AM

This reminds how the DC has the worse S-video output of all the common consoles. Really bad dot-crawl even with still pictures. Hell look at the Sega logo screen when a game starts up. I do use generic S-video cables from NCSX.com.

Does anyone get different results from official cables or the S-video output on certain VGA boxes?

I am this close to buying RGB cables and getting an RGB to Component converter for all my 16-128 bit systems.

SNKNostalgia · 02/10/2010, 06:19 PM

bump

I am wondering if anyone knows the answer to my question. It still bothers me that the s-video is crappy with the DC S-vid cable.

Joe Redifer · 02/10/2010, 07:59 PM

Your s-video cable could have the same fault as many SNES s-video cables... deriving the signal from the composite pin. Cheap-o cables are never, ever the way to go. The problem is your cable, guaranteed.