Scaling .sup Subs

[koberulz]

I have a .sup file from a BD I want to mux into the video from a UHD, and vice versa.

BDSup2Sub seems to offer scaling, but it just seems to want me to enter a target resolution without entering a source resolution, which seems weird, and maxes out at 1080p anyway.

Are there other options?

[Ennio]

Note that SUP on UHDBD is authored in 1080p. To be compliant as for size, there's no need to scale them. I can even imagine players expecting 1080p SUP for 4K would accidentally scale up already 4K scaled subs. Should you want to use them for HDR video, I do suggest to lower the luminance of the subtitle images. Subtitle Edit has a tool built-in its SUP editor for doing so.