I have been looking all over for some software that will convert .264 files that my Swann CCTV recorder saves. The apps that Swann offer are not that good on the Mac, mostly because the app tends to freeze making mostly unusable.
The best software I have found so far that is pretty good and will convert .264 files to either .mp4 or .mkv.
There are versions for IOS, Windows and Ubuntu
If the link doesn't show below, the just search the web for Handbrake
The software is open source so therefore free
https://handbrake.fr/downloads.php
JJ