Dreamcast S-video 480i alternating fields are wrong

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  • August 25, 2020 at 4:55 AM #40978
    AJBats
    Participant

      I just recieved my Koryuu, which I bought for my dreamcast. I hooked up the DC through S-Video to the Koryuu, and then the output component cables are hooked up to a standard consumer CRT TV set.

      The result are alternating fields, but they are synced up on even (or odd) rows. This results in the image looking both like 240p, and shimmers like 480i. I’ve tried many times to get a image with a camera, but no luck.

      I did notice this note from the wiki:
      “Interlace signal field reversal – Intermittently, the Koryuu will reverse the fields in an interlace signal (odd field will be switched with the even field).
      This can cause compatibility issues with the OSSC or other undesirable effects on CRT displays. Usually, power cycling the unit or switching to a different input will cure the problem.”

      This certainly sounds like what is going on, however the workaround suggested here is not working. I will turn off and on the koryuu, no luck. I also turn it off and unplug it for 10 seconds, and also no luck.

      Any ideas?

      August 27, 2020 at 5:43 PM #41046
      BuckoA51
      Keymaster

        It is something we’re looking into, you might need to power cycle Koryuu a number of times before it locks on correctly.

        Though I’m curious as to why you would use a Koryuu on a Dreamcast when component video cables are available?

        August 28, 2020 at 11:07 PM #41090
        nmalinoski
        Participant

          Though I’m curious as to why you would use a Koryuu on a Dreamcast when component video cables are available?

          Only thing I can think of is a desire to play the handful of titles that don’t support RGB output (as in composite-/S-Video-only) without a patch. (That would also preclude use of HD Retrovision’s cables, which appear to require RGB.)

          September 10, 2020 at 3:11 PM #41289
          megari
          Participant

            I am testing a version of the firmware that I’m hoping will help with various issues related to interlacing and transitions between interlaced and progressive modes. If you’re willing to give the test firmware a try, please feel free to send me a message!

            September 15, 2020 at 1:03 PM #41360
            megari
            Participant

              A new test version of the Koryuu firmware was released this week. I would be very interested to learn if it has improved the NTSC field reversal problem. Would you be willing to try it?

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