New install of Fedora 38.
Installed for video thumbnails:
I have deleted the contents of ~/.cache/thumbnails several times and restarted Files.
Despite this, only a few thumbnails out of many are displayed. I have been searching for solutions for 2 days and have still not solved the issue. I am surprised this is so complicated on such an advanced system as Fedora. Any help much appreciated.
Did you try gthumb:
sudo dnf install gthumb
Unfortunately still the same.
Do you have examples of extensions/video type you like to see?
So you are looking to a thumbnail of the content of the Video or you just would like to see which app is open it.
If you have examples we probably can check if it works with our setup.
No thumbnails for .mp4 videos. Thumbnails do work for webm, .flv, gif, mpeg, avi. However, there are also many .flv that do not have thumbnails.
Strangely, very few mp4 vids do have thumbnails. I checked the properties and the seem to be the same:
Are your videos on your computer or on a external storage in the network?
If External you might change the preferences>show thumbnails>all files in Gnome Files.
They are on my computer and I set show thumbnails to all. Still no love.
I do not have more ideas than the last link:
There is as section how you can debug/troubleshoot if needet.
Thanks for that link. It was very detailed. I went through all the steps and have some clues but have not solved the issue yet. Below I will print the debug log of Nautilus when creating thumbnails for successful ones and unsuccessful ones. I am not able to figure out what the problem is. Maybe you can.
This one did NOT create a thumbnail:
(totem-video-thumbnailer:2): GLib-GIO-DEBUG: 18:36:26.015: _g_io_module_get_default: Found default implementation local (GLocalVfs) for āgio-vfsā
(org.gnome.Nautilus:22776): GnomeDesktop-DEBUG: 21:36:26.133: About to launch script: bwrap --ro-bind /usr /usr --ro-bind-try /etc/ld.so.cache /etc/ld.so.cache --symlink /usr//bin /bin --symlink /usr//lib64 /lib64 --symlink /usr//lib /lib --symlink /usr//sbin /sbin --setenv GST_REGISTRY_1_0 /home/me/.cache/gnome-desktop-thumbnailer/gstreamer-1.0/gstreamer-1.0.registry --bind /home/me/.cache/gnome-desktop-thumbnailer/gstreamer-1.0 /home/me/.cache/gnome-desktop-thumbnailer/gstreamer-1.0 --ro-bind-try /etc/alternatives /etc/alternatives --proc /proc --dev /dev --chdir / --setenv GIO_USE_VFS local --unshare-all --die-with-parent --setenv G_MESSAGES_DEBUG all --bind /tmp/gnome-desktop-thumbnailer-G72P61 /tmp --ro-bind /home/me/Videos/smalldog.mp4 /tmp/gnome-desktop-file-to-thumbnail.mp4 --seccomp 14 /usr/bin/totem-video-thumbnailer -s 256 file:///tmp/gnome-desktop-file-to-thumbnail.mp4 /tmp/gnome-desktop-thumbnailer.png
This one DID create a thumbnail:
(totem-video-thumbnailer:2): GLib-GIO-DEBUG: 18:36:25.178: _g_io_module_get_default: Found default implementation local (GLocalVfs) for āgio-vfsā
(org.gnome.Nautilus:22776): GnomeDesktop-DEBUG: 21:36:25.254: Failed to launch script:
(org.gnome.Nautilus:22776): GnomeDesktop-DEBUG: 21:36:25.255: About to launch script: bwrap --ro-bind /usr /usr --ro-bind-try /etc/ld.so.cache /etc/ld.so.cache --symlink /usr//bin /bin --symlink /usr//lib64 /lib64 --symlink /usr//lib /lib --symlink /usr//sbin /sbin --setenv GST_REGISTRY_1_0 /home/me/.cache/gnome-desktop-thumbnailer/gstreamer-1.0/gstreamer-1.0.registry --bind /home/me/.cache/gnome-desktop-thumbnailer/gstreamer-1.0 /home/me/.cache/gnome-desktop-thumbnailer/gstreamer-1.0 --ro-bind-try /etc/alternatives /etc/alternatives --proc /proc --dev /dev --chdir / --setenv GIO_USE_VFS local --unshare-all --die-with-parent --setenv G_MESSAGES_DEBUG all --bind /tmp/gnome-desktop-thumbnailer-E0XQ61 /tmp --ro-bind /home/me/Videos/demello.mkv /tmp/gnome-desktop-file-to-thumbnail.mkv --seccomp 14 /usr/bin/totem-video-thumbnailer -s 256 file:///tmp/gnome-desktop-file-to-thumbnail.mkv /tmp/gnome-desktop-thumbnailer.png
Then I tried to manually create a thumbnail in verbose mode. Below are one that worked and one that didnāt.
Did NOT work:
[me@fedora Videos]$ totem-video-thumbnailer --size 256 --verbose ~/Videos/chaka.mp4 chaka.png
TotemVideoThumbnailer-Message: 21:33:21.272: Initialised libraries, about to create video widget
TotemVideoThumbnailer-Message: 21:33:21.274: setting URI file:///home/me/Videos/chaka.mp4
TotemVideoThumbnailer-Message: 21:33:21.274: Video widget created
TotemVideoThumbnailer-Message: 21:33:21.275: About to open video file
TotemVideoThumbnailer-Message: 21:33:21.350: Checking whether file has cover
TotemVideoThumbnailer-Message: 21:33:21.350: totem-video-thumbnailer couldnāt find a video track in ā/home/me/Videos/chaka.mp4ā
DID work:
[me@fedora Videos]$ /usr/bin/totem-video-thumbnailer --verbose -s 256 ~/Videos/demello.mkv ~/Videos/chaka.png
TotemVideoThumbnailer-Message: 07:01:43.024: Initialised libraries, about to create video widget
TotemVideoThumbnailer-Message: 07:01:43.027: setting URI file:///home/me/Videos/demello.mkv
TotemVideoThumbnailer-Message: 07:01:43.027: Video widget created
TotemVideoThumbnailer-Message: 07:01:43.027: About to open video file
TotemVideoThumbnailer-Message: 07:01:43.103: Checking whether file has cover
TotemVideoThumbnailer-Message: 07:01:43.103: Opened video file: ā/home/me/Videos/demello.mkvā
TotemVideoThumbnailer-Message: 07:01:43.103: About to seek to 0.333333
TotemVideoThumbnailer-Message: 07:01:43.104: About to get frame for iter 0
TotemVideoThumbnailer-Message: 07:01:43.107: Frame for iter 0 is interesting
TotemVideoThumbnailer-Message: 07:01:43.108: Saving captured screenshot to /home/me/Videos/chaka.png
totem-video-thumbnailer couldnāt write the thumbnail ā/home/me/Videos/chaka.pngā for video ā/home/me/Videos/demello.mkvā: Failed to open ā/home/me/Videos/chaka.pngā for writing: Permission denied
That it failed to save the thumbnail is not important to us here as it shouldnāt have permission to write here. What is important is it did create the thumbnail.
Maybe you can make some sense of this as I cannot. Thanks
Ok, I finally found the solution in case anyone else is struggling with the same problem. The problem is that Totem thumbnailer does not work correctly. The solution is:
sudo rm -r ~/.cache/thumbnailers/
I donāt know why Fedora is including faulty software in their releases.
Because users as you ask for help and when they find an error they not report it 
Where should I report it?
Just check if you find something before file a new bug. I had a quick look and could find nothing specific.
It was way too complicated with new sign-ins and so on. No wonder many donāt report stuff. I may look into it again when I have more time.
If everyone had that attitude no problems would get reported and nothing would change.
I encourage everyone to stretch just a little and make what effort they can to report noted problems with as much information as is possible. This helps the developers to identify needed fixes.
Thanks for finding this solution. I was scratching my head as to how to remove totem from the thumbnailers folder until trying sudo rm -r totem-thumbnailer or something along those lines.