SNES video/audio randomly cuts out in HDMI mode but not DVI

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  • #41266
    euan
    Participant

    Hello, I recently upgraded my firmware from I think 0.82 to 0.86. Until now I had my audio routed straight to my TV and TX Mode set to DVI, because of some sort of incompatibility between my TV and older OSSC firmwares with TX Mode set to HDMI. However, to get audio working with my TV and my new-to-me PSP I had to route audio through the OSSC and set TX Mode to HDMI (I saw there were fixes to this mode in firmware 0.84).

    With the PSP and PS2 this seems to be fine, but I’ve noticed that with my SNES the video and/or audio will randomly cut out briefly from time to time. This never happened with TX Mode set to DVI. The light on the OSSC stays green I believe when either one (or both) cut out, and the cut outs are very random: sometimes there will be like 40 minutes between them, and sometimes as little as 45 seconds between them. There hasn’t been any correspondence I’ve noticed between what’s happening in the game (either audio or visual) and these cutouts. The game I’ve been playing is Final Fantasy II/IV.

    As a workaround, I could route audio from my SNES to my TV and set TX Mode back to DVI for that profile while leaving everything else set to HDMI and routing their audio to the OSSC. But, I’m wondering if I have some other setting wrong that I need to fix.

    My setup is SNES -> SNES HD Retrovision cable -> gcomp -> male-to-male HD Retrovision cable -> OSSC -> HDMI switch -> TV

    Here’s my SNES settings:

    
    {
        "version": "0.86",
        "main": [
            {
                "profile_name": "Super NES",
                "video_lpf": "Auto",
                "ypbpr_cs": "Rec. 601",
                "r_f_off": "128",
                "g_f_off": "128",
                "b_f_off": "128",
                "r_f_gain": "26",
                "g_f_gain": "26",
                "b_f_gain": "26",
                "c_gain": "8",
                "clamp_offset": "128",
                "alc_v_filter": "10",
                "alc_h_filter": "3",
                "s480p_mode": "Auto",
                "s400p_mode": "VGA 640x400@70",
                "tvp_hpll2x": "On",
                "upsample2x": "Off",
                "sync_lpf": "2.5MHz (max)",
                "stc_lpf": "4.8MHz (HDTV/PC)",
                "sync_vth": "11",
                "linelen_tol": "6",
                "vsync_thold": "68",
                "pre_coast": "1 lines",
                "post_coast": "0 lines",
                "pm_240p": "Line5x",
                "pm_384p": "Line2x",
                "pm_480i": "Line2x (bob)",
                "pm_480p": "Passthru",
                "pm_1080i": "Line2x (bob)",
                "l2_mode": "Generic 4:3",
                "l3_mode": "Generic 4:3",
                "l4_mode": "Generic 4:3",
                "l5_mode": "256x240 optim.",
                "l5_fmt": "1600x1200",
                "ar_256col": "4:3",
                "tx_mode": "HDMI (RGB)",
                "hdmi_itc": "Off",
                "sl_mode": "Off",
                "sl_str": "0",
                "sl_hybr_str": "0",
                "sl_method": "Multiplication",
                "sl_altern": "On",
                "sl_id": "Top",
                "sl_altiv": "Off",
                "sl_type": "Horizontal",
                "sl_cust_l_str_1": "0",
                "sl_cust_l_str_2": "0",
                "sl_cust_l_str_3": "0",
                "sl_cust_l_str_4": "0",
                "sl_cust_l_str_5": "0",
                "sl_cust_c_str_1": "0",
                "sl_cust_c_str_2": "0",
                "sl_cust_c_str_3": "0",
                "sl_cust_c_str_4": "0",
                "sl_cust_c_str_5": "0",
                "sl_cust_c_str_6": "0",
                "h_mask": "0",
                "v_mask": "0",
                "mask_color": "Black",
                "mask_br": "0",
                "reverse_lpf": "3",
                "full_tx_setup": "Off",
                "vga_ilace_fix": "Off",
                "av3_alt_rgb": "Off",
                "panasonic_hack": "Off",
                "default_vic": "0",
                "audio_dw_sampl": "Off (fs = 96kHz)",
                "audio_swap_lr": "Off",
                "audio_gain": "12",
                "link_av": "No link",
                "export_enabled": "true"
            }
        ],
        "timing_tweaker": [
            []
        ]
    }
    

    Thanks very much for any help you’re able to give me!

    #42593
    euan
    Participant

    To update here, in case anyone else runs into this:

    I was able to mostly solve this by increasing Sync Vth to 236. That’s the biggest number before the image starts to be affected in my setup. I’ve still seen a couple of instances of losing sync since then (OSSC light goes red) but it’s been significantly reduced.

    From googling around more, I stumbled onto threads like this one: https://videogameperfection.com/forums/topic/black-screen-in-yoshis-island-snes/ and https://videogameperfection.com/forums/topic/snes-ossc-fw-0-83-de-jitter-mod-sync-keeps-dropping/. I didn’t realize that the game would make a difference, so it turns out I’d changed more variables than I thought :). The DVI/HDMI thing was a red herring: the sync drops only seem to happen during the battle screens of Final Fantasy 2/4 and 3/6 for me — other games are fine. I’m back using HDMI and things are mostly fixed.

    #42669
    BuckoA51
    Keymaster

    Is your SNES de-jittered?

    #42676
    euan
    Participant

    No, but I’m using the HD Retrovision cables which I believe do some amount of dejittering themselves: https://www.hdretrovision.com/jitter

    I have no idea how to compare the amount or type of dejittering done by the cables vs the mod — do you know?

    FF 2/4 and 3/6 are the only games that have given me an issue so far though!

    #42704
    Harrumph
    Participant

    If the problem is due to your display not liking the SNES sync jitter, then I don’t believe the HD retrovision anti-jitter system cannot help. Their fix attempts to correct horizontal sync jitter on the rising edge (which is a more general case, affecting many consoles on some specific displays component input) while the root of SNES specific jitter is on the vertical sync, where NTSC SNES is missing one clock cycle every other frame.

    #42711
    euan
    Participant

    The light on my OSSC goes red during the remaining desyncs, I believe, so I don’t think it’s my display. But thanks for the additional information on the different kinds of dejitter — that’s very interesting!

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