I've got a bunch of movies in a folder that's on a laptop running a Plex server. Some movies play fine, and others don't buffer at all.
Is there an FFMPEG conversion command that will convert them all to a format that Plex will just play natively?
Plex provides list of supported media formats (albeit a bit hidden) for Smart TVs, and games consoles on their web pages but not for windows or Mac as far as I am aware - I think the logic is that they support everything but some things need to be transcoded.
They do provide (again well hidden) an example ffmpeg command line here at https://support.plex.tv/hc/en-us/articles/201358273:
ffmpeg -i inputfile.mkv -crf 18 -map 0 -acodec copy -scodec copy -c:v libx264 -threads 0 -preset veryslow outputfile.mkv
You can also use plex itself to look at the media format, in a similar way you might use probe: https://support.plex.tv/hc/en-us/articles/201998867-Investigate-Media-Information-and-Formats