Often one has a video file that one cannot view - maybe from a CCTV system. It is quite common to be H264 or similar, but does not have a standard wrapper, eg .MOV, or .MP4.
The very good free program VLC does have a feature to allow you to do this. The following Youtube link does describe how to
As a very quick summary, the following may help
- At the bottom select 'All'
- In Stream output select 'Muxers'
- Then select the Mux module - (Automatic is the default)