OSSC and Genesis sync quirk with assorted games

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  • #25523
    netarchy
    Participant

    I’ve noticed that a number of games exhibit a few sync drops/changes during startup, for instance, pick just about any Konami game, like Castlevania Bloodlines, or TMNT the Hyperstone Heist, and the sync will drop briefly during the startup where you would see the sega logo followed by the Konami jingle (and it will happen every time the Konami jingle comes back around). Several other games do this as well. My tv recovers relatively quickly, though my Avermedia GC573 takes a bit longer to resync every time this happens, and in both cases I end up missing pieces what’s going on until the sync is re-established.

    I don’t recall ever seeing this on the framemeister, is there some setting I’m perhaps missing that I can tweak on the OSSC to cut this behavior out?

    #25524
    Harrumph
    Participant
    #25525
    netarchy
    Participant

    H-PLL coast makes certain modes like the split screen in Sonic 2 work, doesn’t seem to do anything for the quirk I’m talking about through.
    Is it possible that these games are actually doing some resolution switching specifically for the intro segments?
    ie; Res Switch -> Sega logo -> Res Switch -> Konami Logo -> Res Switch -> Game title screen

    #25527
    Harrumph
    Participant

    That is certainly possible.
    According to FirebrandX’s list of 256×224 games, at least Hyperstone Heist will switch because the Sega logo is in 320×224 mode. However, Castlevania is not listed.
    http://www.firebrandx.com/OSSC/Genesis%20256%20Mode%20List.txt

    #25528
    netarchy
    Participant

    Ah hah! That’s what it is then! The TV recovers very quickly and cuts out nothing, but the capture card takes longer to re-sync up so it misses good chunks while it switches resolutions.
    I suppose that solves the mystery then, not really anything to be done about it.
    Could be worse.

    #25529
    nmalinoski
    Participant

    If you need a consistent image for streaming, you should get one of those cheap SCART->HDMI adapters (and a SCART splitter if you don’t have a gscartsw with a second output).

    It’s not the OSSC at fault per se; rather, it’s HDMI dropping sync because something in the video changed, either the resolution or the framerate. That causes HDMI to disconnect and everything in your chain to renegotiate. In order to avoid dropouts, you need a scaler with a full framebuffer that can both perform framerate conversion and continually output at a predefined resolution and framerate. Yeah, it would probably add at least a frame of lag, but that will be the tradeoff. (Use a CRT, play with lag, or play with dropouts–pick one.)

    QMS in HDMI 2.1 should help to an extent by eliminating dropouts for framerate changes, so a scaler, like the Framemeister, that is configured to consistently output 1080p for all video modes, could be able to run without dropouts; however, I’m pretty sure that will need HDMI 2.1 on both ends, meaning new hardware revisions of the OSSC and/or Framemeister will be needed to take advantage of it.

    #25530
    netarchy
    Participant

    I’m thinking a scart splitter. One to my OSSC, one to my framemeister, framemeister outputs to capture card, ossc to tv, play on tv, stream capture without dropouts, best of both worlds 😀

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