Question: Video files do not have sound upon import into iMovie?
I have recently updated my MacBook Pro's operating system to High Sierra. When I tried to go into iMovie and upload a few of my MP4 (MPEG-4) video files, some of them do not have sound! I tried troubleshooting on my own but could not find any help. What could be the reason that some of them have sound upon importing, while others don't? All of them have sound when played outside of iMovie. Any help would be appreciated.
MacBook Pro with Retina display, macOS High Sierra (10.13.3)