I just bought an S7. It produces .mp4 files and Hitfilm Express 4 wont support it. I had similar problems with .mov files from imovie or from iPad. (Solved after installing Quicktime)
With Android, Asus Zenfone Selfie, I had variable fps issue, that led to terrible audio video sync issues.
I do not want to convert the footage to one single thing because I've a very slow computer, a windows 10 pc. It takes ages. Why cant Hitfilm work with it directly? Somebody please help.
Update: As I've said in the comments, I am waiting for an answer to which file format is best for editing. Handbrake just gives option of .mp4 and .move is not supported by hitfilm express 4.
Increasing the project setting fps to 32fps allowed me to import S7 footage with 30.013 fps and I then changed it. Thank you everyone for taking the time to comment. And the comment on asking me to buy the software instead of S7 has been removed. Was it the moderator? Thanks.