CRT Sync with some games

Questions about the RaspberryJAMMA adapter.

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tonyperkwx
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CRT Sync with some games

Post by tonyperkwx » Tue Aug 20, 2019 4:03 pm

I'm not sure if this is a hardware or software issue, but curious if other have run into this too. I'm running MAME2003 (0.78) on a Pi3, using a CRT arcade monitor. It's set to low rez and everything works great for all but one of the 25 or so classic vertical games I have on there.

I have an issue with Burgertime when it comes to video. It displays properly for about 7-8 seconds, then the screen goes dark and it comes back up with a resyncing type of flutter momentarily. Then it's fine for about about another 7-8 seconds and it repeats, and on and on. I haven't tried it with a LCD or another version of MAME to see if the result is the same.

I haven't seen this on any other games. I'm a little baffled what could be causing this.

dee2eR
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Re: CRT Sync with some games

Post by dee2eR » Wed Aug 21, 2019 12:50 am

I don't think I've seen that behaviour before, but I don't know if I've tried Burger Time in MAME 0.078 before. Hard to say what the problem may be.

It should run well in MAME 0.106 (AdvMAME). May be worth trying it in that emulator.

tonyperkwx
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Re: CRT Sync with some games

Post by tonyperkwx » Mon Sep 02, 2019 3:12 am

I tried a few more tests when I can to swap out components and narrow down the issue. Here's what I've found:
1. The same problem exists for mame2003 and advmame.
2. It exists on all 3 variations of btime rom sets.
3. Both the video and the sound go out when the problem happens. Gameplay continues as I can hold the joystick a direction and when the picture appears again Peter has moved as expected.

4. Using VGA out from the DAC to a VGA monitor instead of into ArPiCade's VGA port, with retropi set to 480p resolution as anything less doesn't output to the monitor, it works fine. All but the video still routes through the ArPiCade including sound and controls and it works fine. No warning messages or anything appear intermittently that could be hosing up the display.

5. Using output from Pi to HDMI, with retropi set to 240p, to a LED TV works fine. The TV says it's using 960x240p. No warning messages or anything appear intermittently that could be hosing up the display. Gameplay control is fine.

So this is the weird one:
6. Using everything set up as complete to ArPiCade except for the sound input - The sound output from the DAC instead goes to an external speaker system. The problem still occurs, and when the video goes out, the sound to the external system also goes out!
This would seem to pin the issue squarely in the Pi and DAC as the sound hangs without ever setting foot into the ArPiCade.

I know the DAC works fine in this use case:
Pi -> HDMI -> DAC -> VGA at 480p is fine.

And Retropi 240p is fine in the use case:
Pi -> HDMI -> LED TV is fine at 240p.

The combination of the Pi at 240p and using the DAC seems to be the problem. With one game. BTW the CRT can't do 480p as a test.

I may be able to swap it for another DAC I can find as a final test. It's kind of like the video output is being switched by the Pi or DAC to show a notification or error message briefly, except it doesn't happen with other video out methods. Still baffled here!

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Re: CRT Sync with some games

Post by dee2eR » Mon Sep 02, 2019 6:05 am

Sounds like the DAC may have an issue with 240p@57.5hz, I don't think I've had one before that was OK in all but one resolution though so it's a bit wierd. If you can try another DAC that would be a good idea. Also it may be worth trying some other games that run at similar frequency, I doubt it's just Burger Time. Snow Bros. should be using the same video mode as Burger Time it maybe worth checking if it behaves the same.

tonyperkwx
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Re: CRT Sync with some games

Post by tonyperkwx » Mon Sep 02, 2019 2:44 pm

Great suggestion. Snow Bros being a horizontal game plays at 480i on my vertical monitor and is fine. If I take the monitor rotate out of the config.txt, then Burgertime plays pretty much fine at 480i (sideways) while Snow Bros now at 240p has the same problem of video going out. Burgertime did show a video glitch or two but for the most part did not for long stretches.

Isn't there a way to set resolution on a game by game basis in retropi? If I can force certain games to 480i while not rotated that would solve the issue. I like the authentic look of 240p too much make it a system wide setting.

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Re: CRT Sync with some games

Post by dee2eR » Tue Sep 03, 2019 11:30 pm

No idea if you can adjust resolution per game in RetroPie, I don't use it.

In ARpiCADE the script /boot/launchers/resSwitch.sh controls the res switching. Rather than set the 240p@57.5Hz games to use 480i you're better off using 240p@60. Make a back up of resSwitch.sh first (because if you mess up this script the system will probably not work right anymore). If you use Windows use Notepad++ to edit the script. Find this bit:
#### is refresh rate between range of 57 - 58 fps
if [ $(lessThan $r 57.00) == n ] && [ $(lessThan $r 58.00) == y ]; then
echo switching to 240p@57.5
vcgencmd hdmi_timings 1920 1 113 192 175 240 1 6 3 16 0 0 2 57.500 0 37560000 1
tvservice -e "CEA 65 HDMI" & sleep 3
fbset -depth 8 && fbset -depth 16
fbset -g 960 240 960 240 16
else
and either hash out or delete it. Now the system will use 240p@60 for Burger Time (and similar refresh rate games).

Seeing your DAC doesn't like 57.5Hz I would still recommend trying another DAC. May be worth contacting the point of sale about it (if a recent purchase) or contact me via PM, I'm waiting on a DAC delivery but am happy to supply one that works properly at all resolutions when I get them.

I hope that helps.

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Re: CRT Sync with some games

Post by tonyperkwx » Sat Sep 07, 2019 3:33 pm

Thanks, that did the trick! No need to mess with the DAC anymore, this is sufficient.

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