That's the thing. Files aren't thumbnailed even if they change, like
when they finished being downloaded with Transmission. Also, if you open
a directory with videos before installing their necessary codecs you
will get the generic icons, and installing the codecs afterwards will do
no good.
nautilus compares the image and thumbnail timestamp to update the
thumbnail that should be working, there is already a bug about adding an
option to manually retry the thumbnailing
--
re-generate failed thumbnails
https://bugs.launchpad.net/bugs/346657
You received this bug notification because
thank you for your bug report, doing thumbnails take quite some
ressources and there is no reason to retry again and again thumbnailing
files which didn't work if they didn't change
** Changed in: nautilus (Ubuntu)
Importance: Undecided = Wishlist
** Changed in: nautilus (Ubuntu)
