Importing over 100k videos and photos and videos go super slow on import and many do not import

It just sites at "import files at their current location".  If i cancel, it shows many videos were not able to be imported.  Docs say that failed imports are logged so canceling shouldn't mean that on the next import the same files are attempted for re-import.  Is there a codec issue?  I'd be ok skipping videos but when you select a top level folder there isn't an easy way to specify file types or extensions to ignore.  I think if i kept import going for the next couple of weeks, i'll see progress but know there must be a way to minimize time it takes to go through the videos.  Photos, on the other hand seem to import at a reasonable rate.