Video shot with Camera App and saved in Photos not working in iMovie
I have an iPhone 12ProMax and have been shooting video using the Camera app. The videos are viewable in Photos and Quicktime. They have the extension .mov (and are being shot in 4K). When I try to make a movie using iMovie (v.10.2.5) the video clip shows in my Media tab but when I try to play it, only the audio is available, the video is a black screen. I am having to convert all of the files to an .mp4 extension which is long and painful. Is there a Camera setting that I can adjust so that both the audio and video taken with my phone is available without conversion in iMovie? Seems that this is defeating the point of using an Apple environment for shooting video and basic editing in iMovie.
Thank you in advance.
iMac 27″ 5K, macOS 10.15