Bright flashes causing loss of sync with OSSC

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    Bill Main

    Hi guys. I’ve had this issue for some time and I’m grateful for all the help Matt & Ari have given me with it. I thought I’d post here in case anyone else has the same issue or has any suggestions to help.

    So basically I have my 3DO & CD32, both standard PAL consoles, connected to the Koryuu via S-Video. The problem I have is whenever there is any bright white flash on screen, the OSSC loses sync for a second or so causing a blank screen. It’s completely predictable and easily replicated (smart bomb on Microcosm CD32, death in D/Generation CD32, mid level save Gex 3DO and several others)

    We have tried lots of troubleshooting. Having only the sync output (green) from Koryuu connected to OSSC still happens, connecting composite instead of S-Video still happens.
    Ari provided several tweaked firmwares to try but sadly no difference.

    I’ve been able to connect the Koryuu directly to Component input on two different TV’s and everything works fine, no image loss. This made me think the issue was with the OSSC.
    We then connected just the composite outputs from both consoles directly to the sync of the OSSC and there is no drop (albeit image is black & white) This seems to suggest it is something output from the Koryuu.

    Marqs suggested tweaking some filters but it made no difference. It’s the strangest issue and I think we are all a bit stumped with it.

    I’m putting this post up in the hope someone may have some suggestions or have also experienced this issue.


    Hi Bill!

    Indeed, the issue you are experiencing is quite a mystery. As you detailed above, the results of the troubleshooting ended up being inconclusive, as they pointed to the OSSC on one hand and to the Koryuu on the other. Also, if I remember our correspondence correctly, there were also differences between displays (although this is rather common when the video source is a retro console/computer)?

    However, when looking at all the identified configurations with this issue, the only constant factors seem to be the bright flashes (even with just luma+sync), the consoles themselves and the Koryuu. I am quite puzzled by what could cause this, as even the brightest flashes should not affect sync when the physical characteristics of the video path are correct, as I remember us spending quite a bit of effort confirming.

    Bill Main

    Hey Ari,

    Yeah, it’s really strange and as you say some testing led us to the OSSC being the issue and others led to the Koryuu.
    I just thought I’d put a post out in case there were others who had similar issues or a solution.

    On the other hand, it’s made me have to get better at some games as using a special weapon causes sync loss so can’t rely on that to get me out of trouble 😂
    Anyway, maybe someone has an idea that we’ve not tried but for the moment I’m just living with it.

    Josue Castaner


    I don’t have much to add as a solution but I’ve been experiencing the same issue (maybe). I have a koryuu and an OSSC. I use the koryuu for my NES via composite and the N64 via svideo. Both consoles are NTSC and I’ve been seeing the same loss of sync with my setup. I have an LG55BX TV and was able to take a screenshot of the issue. I was playing Shadows of the Empire and I kept losing sync whenever there were bright scenes. It happens fairly often and always happens when using the koryuu (I haven’t seen it happen when using the OSSC by itself). This is the link to the screenshot.

    Looking forward to a solution!


    Try as we might we were never able to reproduce the issue I’m afraid. I tried the same games as Bill in the same places and never had a problem.


    Same issue here.

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