Compatibility mode?

NewHome Forums OSSC & OSSC Pro OSSC – Feature Requests Compatibility mode?

Viewing 15 posts - 1 through 15 (of 17 total)
  • Author
    Posts
  • #26387
    Trixster
    Participant

    Is there a possibility of providing a compatibility mode for those of us stuck on fw 0.76?

    “For some reason those reported displays seem to accept 628-line signal if sync/enable signal is formatted somewhat incorrectly (as can be done with the posted settings on 0.76). I’d need check resulting timings and then perhaps provide a compatiblity option to enable such deranged sync on later fw.”

    The problem is detailed in this thread:

    PS2 240p RGB doesn't work

    #26461
    marqs
    Participant

    It’s on TODO list, maybe I have some time to check after getting v0.83 released. Unfortunately I don’t have my old VT50 anymore which could be used to test this, but maybe I can first make a variant out of the display test firmware which would have the necessary hack enabled.

    #26808
    marqs
    Participant

    Tonight I checked which kind of output v0.76 produces with the mentioned settings. There are a couple things off with resulting sync, but most prominent one is that data enable signal ends up overlapping vsync which cannot occur in later firmwares. I made a temporary change enabling this on the latest fw and uploaded a test image here. Please try that PSX 288p in line2x mode with V.active set to 300 as mentioned in the linked thread. You may then also need to adjust V.backporch to make the signal recognizable by the TV.

    #26820
    Trixster
    Participant

    Hi Marqs,

    Thanks for trying to resolve this. I’ve just tried the test firmware with my GT50 Panasonic. Sadly it didn’t resolve the issues 🙁

    I tested with a PAL PS1, a PAL PS2 and a UK 60hz modded Neo-Geo AES. Unfortunately I cannot get a picture when modifying the settings to those which are known to work with fw0.76

    Upon returning to fw 0.76-aud these systems started displaying ok again on this tv.

    Just to clarify – the PS needs v.active of at least 300. The 60hz Neo geo aes requires a v.active of 256

    Is there anything else which you think could be different about post-0.76 that could be stopping pal working on these types of tv?

    Thanks again for your time and efforts!

    #26824
    marqs
    Participant

    Ok, maybe it’s be better to debug this the other way. I made a couple additional changes on the firmware (uploaded to the same file) so that it should now behave just like v0.76 when you use PSX 288p and set V.backporch to 16 and V.active to 300.

    #26830
    Trixster
    Participant

    That seems to have fixed it! Nice one 🙂

    Ps1 and ps2 start to get a picture once v.active is 297 and higher. The neogeo aes also now produces a picture too when v.active is 253 or higher

    Thanks so much for looking into this

    #26831
    marqs
    Participant

    That’s not a final fix yet but a starting point. The next step is to normalize the signal step-by-step to get an idea of minimum number of hacks needed for a compatibility mode option. I just corrected hsync-vsync alignment and re-uploaded to the same file – can you try if it still works with PSX?

    Ps1 and ps2 start to get a picture once v.active is 297 and higher.

    Was that with default V.backporch (19) or with adjusted one (16)?

    #26833
    Trixster
    Participant

    This was with default v.backporch of 19. All that needed to change was increasing v.active.

    I will test the new upload now

    #26834
    Trixster
    Participant

    Ok, that new upload breaks compatibility. Returning to the previous test firmware and I get a picture again.

    #26836
    marqs
    Participant

    I see. I rolled back that change and made another one. If that restored compatibility, could you check what’s the smallest accepted V.active with V.backporch 16 and 10?

    #26837
    Trixster
    Participant

    Ok, this version breaks compatibility.

    #26839
    marqs
    Participant

    Another version uploaded for test.

    #26840
    Trixster
    Participant

    This new version fixes compatibility, and I can lower v.backporch from default 19 right to 1 and I still get a picture.

    And… I can reduce v.active down from the 300 I normally use to get a ps1 picture right down to 260 and lower and I still get a picture!

    The same for neogeo 60hz – I can reduce v.active from 256 back down to 240 and I get a picture

    #26845
    marqs
    Participant

    Finally in the right direction, then. It’s good to hear the default sampling settings are now accepted with the current method which consists of 2 separate hacks (DE cut on last active line and vsync offsetting). I still wonder if the former alone is sufficient so I uploaded one more test version for you to try. After that it’s pretty clear what you have to do with the Panasonics.

    #26846
    Trixster
    Participant

    That new version works great too, on both ps1 and Neo-geo and even with v.active turned back down to default, and with all ranges for v.backporch.

    Can I just check – what is the actual default value for v.active on 240p and also for 288p?

Viewing 15 posts - 1 through 15 (of 17 total)
  • You must be logged in to reply to this topic.