I’ve been playing around with the OSSC + Retrotink2x with a PAL C64 (Reloaded Mk II) too.
The main thing I was interested in was trying to get optimised mode setup. I think I have something, but the picture isn’t clean enough over using the Retrotink2x on it’s own – which does a pretty good job with s-video.
The settings I have for optimised are:
240p/288p proc.: Line5x
Line5x mode : 320×240 optim.
Line5x format : 1920×1080
– H. samplerate: 504
– H. synclen : 63
– H. backporch : 31
– H. active : 384
– V. synclen : 3
– V. backporch : 36
– V. active : 240
Is there a better optimised configuration? Perhaps we need something like 384×272 optimised, which is meant to be the maximum drawable area of the C64 display.
This config is a bit weird because of the way 1080p mode works in 5x, it fills the 16:9 frame by chopping off quite a bit of the horizontal borders. The aspect ratio isn’t right, but it is surprisingly close.
If you wanted 320×240 Optim. in one of the other line multiplier modes, you’d probably need to set H. active to 320, and H. backporch to 63 for it to work (or stand a chance of it working – only 3x did for me), although that cuts off the vertical borders completely.
I think some horizontal tremor is introduced by the HDMI->VGA adaptor and the C64 Reloaded itself, but I don’t know which is most to blame. The Retrotink2x by itself produces a much steadier image, and I haven’t experienced the same kind of shifting as demolition.
Also a GameCube over composite with the same setup (Retrotink2x > HDMI-VGA Adaptor > OSSC) was much steadier in 240p, not perfect, but much less ‘interference’ at pixel edges than the C64.