Video out flickering

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MLConian
noob
Posts: 2

Video out flickering

Post#1 » Sun Mar 28, 2021 8:39 am

My Sony KD-43XE7096 still has composite in, so I hooked my recently bought Dreamcast up to see if it worked. It booted without a hitch, so I tested if it switched between 50Hz and 60Hz modes on a game, which worked perfectly. The tv does create loads of input lag however, so I hooked the DC up to my retro gaming TV, a Panasonic Quintrix TX-21AP2F. This is a TV I've been using for my original Xbox, PS2 (both phat and slim), Gamecube, Wii, SNES, NES and even my wife's Megadrive. It always produces a great picture and doesn't give any problems with 50Hz or 60Hz content.

However, as soon as the Dreamcast boots into a real full-screen game, such as Evolution: the World of Sacred Device in 60Hz mode, or Skies of Arcadia (PAL version), or my NTSC-U copy of Sonic Adventure 2, the top of the screen starts flickering - a band of about 2 to 3 cm. It's mainly noticeable on blues. It doesn't flicker at all if the game is slightly letterboxed, such as the PAL DreamOn demo disc that came with the console or the 50Hz mode of Evolution. At first I thought it was because the DC was displaying 60Hz, but Skies of Arcadia is the PAL version, which I assume runs in 50Hz.

It only does this when it's connected to a CRT - I've also got a 27 inch Logik panel that I know has very little HDMI lag (when I plug in my Wii U and play a Virtual Console game on it, the sound from the TV and the gamepad is fully in sync), so I figured I might as well test that. It doesn't flicker on that at all. I think it's because the TV is doing some de-interlacing, but I'm not sure how to test that (all I know is that N64 games look terrible on it due to de-interlacing artifacts). DC on that TV doesn't look too good however, it's as muddy as you'd expect from an off-brand TV that needs to transform analog to digital. From what I've read online so far, people just shrug it off and say "get a VGA cable, some PAL DCs do this". However, as I bought the Dreamcast especially for Skies of Arcadia, that's not really an option as the game doesn't support VGA. That, and my game room is currently set up so the CRT is the main TV and I don't really have the space to hook up a 27 inch flatscreen and my Dreamcast, and then be able to play on it comfortably.

In short: what could be causing this problem and how do I fix it? Is the video chip shorting out? Is the cable to blame and if so, would a VGA box with composite/S-video out possibly fix this?

MLConian
noob
Posts: 2

Re: Video out flickering

Post#2 » Mon Apr 05, 2021 9:38 am


I managed to capture the issue on video. This is Sonic Adventure 2 NTSC-U on my PAL Dreamcast.

Two things to add here:
- I used S-video cables, hoping a different video signal would solve the issue. That didn't work, the problem is exactly the same.

- I got another Dreamcast to see if it was just my unit, but this one has the same problem as well.

I've also found some people on Reddit with the very same problem, even using the Packapunch RGB cables. This leads me to believe the issue is related to the only pin shared by composite, S-Video and the RGB cables: CSYNC on pin 10 of the Dreamcast AV out. The issue doesn't seem to appear on VGA, and that particular output does not use CSYNC on pin 10 but uses 2 other pins for HSYNC and VSYNC. Could anyone shed a light on this for me, or debunk my theory?

User avatar
slavasnegg
noob
Posts: 2

Re: Video out flickering

Post#3 » Mon Apr 05, 2021 2:19 pm

got the same problem with just one of my three pal Dreamcasts

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