Sorry for the double post.
So, I've started to upscale videos from the Steam version using waifu2x-ncnn-vulkan for videos and srmd-ncnn-vulkan for videos (I'd like to use MMSR but I can't find a decent and stable implementation yet, however it doesn't really matter and I'll explain why).
The main problem I encountered is that videos are natively upscaled to 1080p in the steam version. For videos FMV***.bytes this is not an issue, since they seem to be upscaled decently or simply re-rendered (except FMV060.bytes for some reason). Videso labeled mbg***.bytes are a mess, since they've been upscaled using bicubic. Using a CNN on them "preserves" the bicubic upscaling, giving decent results only when seen on a 4k screen.
I have already upscaled (using super-resolution) every mbg***.bytes video to 4k, plus FMV000.bytes, FMV001.bytes and FMV060.bytes also to 4k.
Another (greater in my opinion) issue is that, regardless of my modification, mbg***.bytes videos do not match the static backgrounds they're swapped from/to (as they did in the original psx version where the transition was smooth and difficult to notice).
As far as I can tell there are 2 (obvious) ways to fix this:
1) adapt the static backgrounds to the videos (easy and probably with a more convincing result)
2) adapt the video to the static backgrounds (may leave a weird "PowerPoint" transition effect)
The effect I'm talking about is most noticeable (because of a completely different color palette, and of course the detail level) when the Alexander staircase appears in front of Dagger (right after mbg111.bytes ends).
I'd try that myself but I have no idea where to get the background images. A package with every background before/after every single mbg***.bytes video would be great.
You probably already know that, but the game accepts 4k videos. The only requirement is that they must use the Theora codec (OGV). Audio track doesn't seem to matter but I'm simply not using that, just like in the original files.