But the advantage of H.265 in terms of disk space is massive so I want that.
But I am afraid of availablilty and performance that made me unable to play those on some computers or future phones and tablets.
What's your idea?
Not all of them but, geez, the space saving... I recently did just that: not every single one of them because I didn't want quality loss on a few specific ones but I had so many files with extensions I don't even the format behind (like .MVI, .MOV) that were just huge. When I mean huge: stuff re-encoded to H.265 and still looking perfectly fine at 1/15th the size! (I think the original files came from some portable video "camcorder", but already digital).
So I wrote a little Bash shell script doing conversion to H.265 (using the x265 codec).
I mean, seriously: family vids / videos filmed with phones aren't going to be used as source material for the next Barbie blockbusters in 8K (or whatever).
I'm not a pro and it's really OK if I take a tiny quality loss on most of these files.
And it doesn't have to be on all the files: I tag a few family videos as "favorites" and these I didn't convert to H.265.
Now even on a 7700X and all cores working at full speed, it takes quite a while: depending on the source format some re-encode super fast (like 12x the speed) while other only re-encode at 2x the speed.
So I just let the script work overnight.
So if your purpose is to archive these files because they're worth keeping, buying a bigger disk may make even more sense.
[Edit] I forgot to add this methodology is also useful if the videos were downloaded from a platform like YT. Future versions of libraries can handle stripping out proprietary meta-data and other garbage from files that was intended for their JS players but useless for archival and local playing purposes.
Chuck everything you no longer need/want (either delete, or push it to cheap storage somewhere)
265 will be standard in a few years. Or so.