

So your files are XAVC wrapped in an MP4 container. Two different things: XAVC is a codec MP4 is a container. So that gives you some things to investigate before someone more knowledgeable joins in. I believe iMovie version 10.07 introduced support for XAVC S. They are XAVC S (or XAVC HS, or XAVC S-I) I don't think your files are MP4 (despite the fact they have. I'm sure I will get at least something wrong: From what I've google'd, it looks like I need to convert the MP4's to something else? Can anyone advise on the best way to do this, or what program to use? Thanks in advance. The files also won't open in quicktime, but will open in an older VLC media player that I had installed.

I've just starting shooting some short video clips and the MP4 files won't open in iMovie. A1 MP4 video files not opening in iMovie.
