I'm trying to combine the burned-in subs of the US disc for The Bourne Identity with the extra scene of the Australian disc, as losslessly as possible.

I can't even find anything that will tell me where the keyframes are, and none of the smart renderers I can find will open it so I can't do it while just re-encoding the small area around the cut.

Thankfully there are no subs after the scene I'm trying to add, so I can just make one cut and switch from the US version to the Australian version and not have to switch back.