Dreamcast-Talk.com

Strap in, this is a long post.



If anyone remembers last summer that I had came across an issue with KOF Evolution where, for some reason it wasn't displaying clean pixels in VGA Mode but hardly anyone else was having that issue.

Here's one of the first posts:

fraggle200 wrote: ↑Fri Jul 21, 2023 3:37 am

fraggle200 wrote:

ateam wrote:
Interesting, my experience is quite different. If anything, they look nearly identical, as DCDigital is taking the 240p input in "cable select" mode and scaling it up per your resolution settings. Meanwhile, the VGA patch (I believe) is just line-doubling 240p to 480p, after which DCDigital would scale that up per your resolution settings.

Even if I'm wrong about the line-doubling, it doesn't make much sense that you're seeing such a discrepancy. I'd be curious to hear if anyone else has the same experience as you.

lemme check on my lunch break.

Well, after some pretty basic testing I've ended up with the same result as @Ant2no78. I'm running DCHDMI HW1 in 1080P for these images.

Here's the VGA output

vga.jpg (29.99 KiB) Viewed 1477 times

Here's the Cable Select output

cable select.jpg (28.28 KiB) Viewed 1477 times

Maybe it's just my eyes but with the Cable Select mode selected you get the raw pixels, which is what I'd have thought we would have got with VGA. Looks like there's some sort of filtering happening to the VGA signal as it's fuzzy/washed out, for the lack of a better term. Looks like in "Terry", we're starting to lose the top and bottom of the lettering when in VGA, compared to Cable Select.

Well, after a lot longer than it ever should have took to get an answer I think I may have some idea what the cause is... although I'm still not 100% sure why.

Between then and now I've tried different:
DC MOBOs
DCDigital HWs, 1 & 2
different DCDigital flex installs
MiniHDMI adapters / cable
hdmi cables
monitors / tv's
SD cards / SSD's in my MODE.
Essentially everything other than a GDEMU to rule out the MODE being the issue. this is where I ended up though as everything else has been swapped out at somepoint.


I've now got a clone 5.20.5 GDEMU and have tried that today as well and the same result happened.... then I stumbled upon something.

This below was all with the GDEMU, unless stated otherwise:

As I had my DCDigital wired to my MODE for the lid automation function, I desoldered the wire and changed the setting back to disabled.

This didn't change anything right away but as I was changing things with KOF running, after disabling the optional wire I put the DCDigital into cable select and then back into FORCE VGA and low and behold..... KOF Evolution was running as it should in VGA.

After realising this, I went back in and set the Optional wire to control the LID on GDEMU/MODE etc and Reset DCDigital from the menu. I didn't reset the DC, just chose restart DCDigital.

Checked KOF Evo and it was back to the fuzzy way it was before.

Feeling pretty smug that I'd solved the issue, I then went back and changed the optional wire back to disabled, reset DCDigital to power cycle it and.... nothing. still the same as before.

I then went in and changed from Force VGA to Cable Select booted up KOF, switched it back to FORCE VGA, restarted DCDigital
and BANG! back to pure VGA for KOF Evo!!!

I've power cycled the DC a few times and it's maintained this.

I swapped in the MODE as I thought that was the culprit before and after booting it up, it was back to fuzzy pixels in KOF. tried what I'd tried above with optional wire & cable select/VGA and it was still the same.

Put my GDEMU back in and it was back to pure VGA in KOF Evo, straight away from a cold boot.



I've absolutely no idea why this is behaving this way but there's a bug somewhere in amongst the gdemu/MODE/DCDigital signal somewhere that's causing it. It just seems like the GDEMU can get around it wilst the MODE can't for some reason.

If anyone has any ideas then let me know but I'm happy I've got to the bottom of it.... kind of, eventually.