Converting Movies for AppleTV
I put a 31 minute-long digitized home movie that I got from a digitizing service as a single mp4 file into my iMac (Ventura), edited them with iMovie (10.3.8) into several smaller movies, and into the AppleTV app for Mac (version 1.3) but they did not show up on my AppleTV under Computers. So, it turns out that AppleTV wants to see mp4 (MPEG-4) movies and not QT movies that iMovie generates. I downloaded the free app HandBrake and used it to convert my .mov files to .mp4 files. Importing them into AppleTV app allowed them to play on my Samsung TV with Apple TV under Computer/Movies. I then learned that the AppleTV app on the Mac will also convert .mov files to .mp4 files when you select a movie and ask Apple TV to "Create iPad or Apple TV version". HandBrake does a better job of converting since it retains the 1250x720 resolution whereas AppleTV app creates a 960x540 mp4 movie file.
There were several erroneous posts stating that just changing .mov to .mp4 would convert your QT movie to MPEG-4. This is wrong. Also, it was suggested that you could use iMovie to save in mp4 format. That is also incorrect. Just either use the AppleTV app on your Mac or download the excellent free HandBrake software and use it to convert your movies.
Apple TV 4K, tvOS 17