re-encoding might change the offset, but not usually.
I did have one where I accidentally changed the framerate slightly so that it wasn't in sync with the music anymore (but it wasn't that bad).
If you only re-encode once, the likelihood of anything messing up is low.
And yes, weezy, windows works via file extension. If you don't give it an extension windows won't know which program to use in order to open the file. Osu will open it just fine without an extension IIRC, but you may as well give it .avi.
I did have one where I accidentally changed the framerate slightly so that it wasn't in sync with the music anymore (but it wasn't that bad).
If you only re-encode once, the likelihood of anything messing up is low.
And yes, weezy, windows works via file extension. If you don't give it an extension windows won't know which program to use in order to open the file. Osu will open it just fine without an extension IIRC, but you may as well give it .avi.