When taking 480p or 512p video that you then line double (960p and 1024p respectively), there are too many scanlines. Basically it appears there’s maybe double the amount of scanlines, and they’re thinner. However, a 240p signal of the same game still has correct scanlines at 4x (960p).
Here’s pictures I took to show how all the other modes appear to be fine: Imgur album
I kept the scanline intensity the same on all the pictures taken.
I don’t know if this potentially affects other modes such as 480i line 4x’ed to 960p (I think you can do that). I haven’t done much testing on interlaced signals.
This is actually the correct/intended behaviour and it seeks to emulate the look of 480p as displayed on a high quality VGA CRT monitor (one that would support higher resolutions, hence the scanlines).
Actually just had a discussion about this with Fudoh over on the Shmups forum. I’d never realized 480p on a CRT would have (much thinner) scanlines.
In this case I think it’d be highly relevant to have an option to switch between the amount of scanlines in 480p/512p line 2x mode. I’m sure I’m not the only one here wanting 240p style scanlines on line 2x 480p (and 512p) that was originally a 240p asset game itself.
You know for the longest time I thought this was a bug until a couple of months ago it struck me. It should probably look that way as 480p x2 gives 480 scanlines correct? In 1x mode it would only be able to give 240 scanlines. But when 480p is doubled you can actually have each scanline take up half of a line doubled pixel, yea? Which is what it seems to do on 240p sources when they are line multiplied. Anyway, I tried 480p x2 using scanlines from the Garo for component and slg3000 for Dreamcast VGA and I don’t feel those look authentic anymore. The scanlines feel too fat like they do in 480i.