0.82a: OSSC wobbles the image on my PSIO-modded PSX on certain games

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  • November 20, 2018 at 11:52 AM #23824
    NRGDEAD
    Participant

      On some of my games, I get a wobbly image when booting them. The vertical pixel rows are shifted horizontally between about 1 and 3 pixels; the intensity is occasionally different. Mostly it’s about one pixel in width. I put together a one minute video to demonstrate the issue.

      I’m running a PAL PlayStation, SCPH-1002, modded for use with the PSIO. It’s using a direct connection to the OSSC via a Retro Gaming Cables UK PS1 CSYNC cable, in the “PACKAPUNCH” variant.
      I first saw the wobble a few weeks ago, when I only had the European/German Demo 1. But then I must’ve switched the PSIO default video mode to NTSC because I liked the visual impression of 240p in 2x better than 576i in passthru. A bit more on that later. I’ve recently switched the default back to PAL, and since updating firmware to 0.82a, I noticed the wobble on my just arrived MechWarrior 2. I tried downgrading to 0.81a, but the wobble also appeared. So I started testing a bit.
      I noticed: when wobbling, the 314p signal is detected as 15.58 kHz, 49.64 Hz. Whereas non-wobbling, the signal is detected as 15.62 kHz, 49.76 Hz.
      The few games I tested and that were affected by this are my Preview Disc 1, also known as Demo 1, MechWarrior 2, Krazy Ivan, Destruction Derby 2 – all in their PAL version, running from my PSIO.
      Metal Gear Solid, Tekken, Tekken 3, Die Hard Trilogy, Alien Trilogy were seemingly not affected.
      The optical disc drive is barely operational on my PSX, which is why I got the PSIO in the first place, so I didn’t bother testing that as well.
      When I switch the PSIO’s default video mode from PAL to NTSC, the wobble mostly does not occur. It did however occur once after switching from PAL to NTSC (not starting up with NTSC) and then running Krazy Ivan.

      While the PSIO might contribute to the wobble appearing, at the moment I think the main issue is the OSSC, since switching inputs fixes the wobble for the game session and/or until the game switches resolutions. Thus I didn’t cross-post to the CybDyn forums yet.

      I’m no expert in video signals, so I’d appreciate any suggestions. If I forgot to provide any key information, please let me know.
      Thanks in advance.

      November 20, 2018 at 2:51 PM #23831
      Steo
      Participant

        My PAL PS1 console has always done that on the OSSC for some reason, then I would just unplug the SCART from the OSSC and plug it back in, then it seemed to stop doing it. I’m not sure what causes it myself but I’m just letting you know I have the same problem.

        Also my PS1 console is just stock with no mods.

        November 20, 2018 at 3:49 PM #23836
        Harrumph
        Participant

          I noticed two things in the video:
          1. You use c-sync cable.
          2. Sync detection on OSSC is unstable.

          This leads me to believe the problem is something fishy with the sync level, possibly related to your RGB cable. I’d mess around with the sync settings on the OSSC first, if you cannot fix it I’d just get a sync-on-luma cable. I’ve never had to mess much with the sync settings but maybe you can get advice from someone else. Also try the forum search function (you need to back out to the main forum).

          August 29, 2019 at 5:12 PM #27732
          NRGDEAD
          Participant

            I since have switched to Sync-on-Luma because I also got myself a Mini Hydra.
            I also upgraded to 0.83a.

            Currently, I still get the wobble when using the Hydra, and not or not so often when connected directly. Of course, I want to use the Hydra to do the switching.
            Since I can switch inputs on the OSSC back and forth to temporarily fix it, and I’m not the only one experiencing this (see the Question regarding PS1 thread), I wonder if anything can be done firmware wise? Maybe prolong the time used to detect the signal or something?

            August 29, 2019 at 6:15 PM #27734
            marqs
            Participant

              I’ve noticed the same problem with PSIO (240p) booting into PAL games (288p). Seems to be another design issue in the TVP7002 digitizer chip, I’m not sure if it can be fixed without negative side-effects (e.g. to 240<->480i switching). Perhaps TVP7002 sync processing reset could be included in mode switch code when “Full TX setup” is enabled, i.e. when compatibility is prioritized over switching delay.

              September 5, 2019 at 10:26 PM #27801
              NRGDEAD
              Participant

                I’d be happy to help testing.

                May 12, 2020 at 8:43 PM #37752
                Aragorn
                Participant

                  I’m having this same issue on 0.85a firmware.

                  No PSIO in my case, just loading games from disk. Some games sync fine and show 49.76hz, others show 49.64 and are wobbly until you switch inputs back and forth.

                  Any updates on a fix?

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