You can easily delete the media cache files using normal OS delete command. Any video file already in Lr catalog are easily removed. Remember to use the 'Remove form Catalog' option not 'Delete form Disk'. In future, the video files can be unchecked in Import window. This prevents them from being imported into Lr. However, you'll need to copy them to your hard disk manually if on a flash card.
there is no way to tell LR to just never import videos into the catalog other than by manually excluding them/removing them with each import?
I found today that I was having a problem with this too. On selecting Bridge to display a load of video files, my C drive filled up, the culprit being this issue I believe. Each video file I selected resulted in a large file being deposited in the cache
I've stopped the LR cache being filled up (unnecessarily as far as I'm concerned) by changing the write permissions to 'Deny' (Using Win 10) for all users, this stops the cache being written to, and as far as I can see, doesn't affect anything I'm interested in
Hope this is of help to others
It's been a while since i originally posted this, so i dont remember the exact folder where the video cache files were stored. But if the video cache files go in the same folder as photos, you might not want to make that folder read-only since it'll probably slow down anything dealing with editing photos as well.
No, its just the video files, which are cached here C:\Users\username\AppData\Local\Adobe\Lightroom\Caches\Video, I've seen no effect on LR after write protecting the video directory