I just bought an OSSC.
I have a SNES (pal version) and a MegaDrive with a pal/ntsc/ntscJ mode selector.
My television is a philips model 32pfl8605h.
I read in the wiki that default line doubling is expected to work with any television,
but I was surprised to see “video format not supported” on my TV when I tried playing with
the MegaDrive in ntsc/ntscj format.
This is the format that is being displayed on the ossc:
With the selector switched to PAL, the television has no problems.
The SNES also has no problems as the video format is different.
My question is: is it normal that my television doesn’t support the
supposedly universal line doubling format?
I had a similar TV model before which would handle a modded SNES in NTSC mode no problem (59.53Hz), so maybe that’s about the limit for vertical refresh rate. I think you might have crossed the tolerance level for vertical refresh with that modded MegaDrive.
A solution would be to get a Dual Frequency Oscillator, to output correct clock speed for NTSC.