This is a weird one because I see it only on certain machines. I work with a lot of mixed pictures and video files in multiple formats. And when I'm working at organizing a bunch of things I've captured, DOpus is my go-to app, given all it's great features. However, when I view a folder containing a mix of such media files in "Thumbnails" mode on some of my machines, all the files display proper thumbnails except QuickTime (*.mov) files.
I've tried clearing the thumbnail cache, refreshing the display, checking the options to make sure it caches them for the type of folder I'm in, etc., but I can't seem to get it to work. Any suggestions? Thanks in advance.
It means there isn't a working thumbnail extractor / demuxer / codec for that format installed on the system. (Or the registry settings for the file type have been broken.) So it's more a general issue than anything specific to Opus.
The FAQ on video files has some suggestions which may work.
I think most newer .mov files are essentially the same as .mp4 files and should be able to work. Older ones have some slight differences which can make them difficult to get working with some demuxers/codecs, in my experience. ("New" and "old" referring more to the software that made them than when they were made.)
Is this page the FAQ to which you refer? The machines that work properly are all much older and no doubt have far more software installed. I'll need to figure out what the new machine is missing.