Hello.
I was wondering why do some mkv files have thumbnails and some don’t (for example “OBS Studio” created files)? Is it not free and opensource format? Is it a bug?
Thank you.
P.S. I am using Silverblue 39
Did you layer ffmpegthumbnailer from rpm-fusion?
No, I did not.
I searched in rpm fusion site for ffmpegthumbnailerbut could not find anything. How to layer it?
Can you run
rpm-ostree search ffmpegthumbnailer
It should return a output like this:
...
ffmpegthumbnailer : Lightweight video thumbnailer that can be used by file managers
...
You can layer ffmpegthumbnailer like other packages with:
rpm-ostree install ffmpegthumbnailer
Additionally, if you need thumbnail support for other formats (like MP4), you might also need to layer libavcodec-freeworld.
Then, reboot and remove existing thumbnails in ~/.cache/thumbnails
1 Like
MP4 files showing up since OS installation.
I installed ffmpegthumbnailer with the command:
rpm-ostree install ffmpegthumbnailer
and deleted files in ~/.cache/thumbnails
It created ffmpegthumbnailer.thumbnailer file in ~/usr/share/thumbnailers
But thumbnails do not show up:
It turns out that libavcodec-freeworld is needed anyway.
rpm-ostree install libavcodec-freeworld
Again, reboot and remove existing thumbnails.
Yes, it worked. Thank you 
P.S. I just can not understand why it is not installed by default in Silverblue?
When I am asking about thumbnails in Gnome forums no one is answering as if it is too hard to answer or actually nobody knows what is going on. It is really strange that there are more talks about new Gnome releases when the old gnome lacking many functionalities for decades. Who cares about dots indicating workplaces in top bar if a simple thing like thumbnails do not work of a free and opensource extensions like blend or mkv. 
mkv is just a container format. The video stream contained within is likely using a patent-encumbered codec that Fedora does not and cannot support by default.
On Workstation, thumbnailing for H.264 may work via openh264, which should be auto-installed starting with F40. That doesn’t help for Silverblue though, or for H.265 videos.
A potential solution would be support for packaging thumbnailers as flatpaks, which you could install from Flathub.
FWIW, it is also possible to add a custom thumbnail to your MKV file. For example, if you have mkvpropedit, you could do it with a command like the following.
$ mkvpropedit my-video.mkv --attachment-mime-type image/jpeg --attachment-name 'cover.jpg' --add-attachment my-thumbnail-640x360.jpg
$ ffprobe my-video.mkv
...
Stream #0:2: Video: mjpeg (Baseline), yuvj420p(pc, bt470bg/unknown/unknown), 640x360 [SAR 96:96 DAR 16:9], 90k tbr, 90k tbn (attached pic)
Metadata:
filename : cover.jpg
mimetype : image/jpeg
Silverblue is a fedora version. They have the same codec restrictions as all fedora spins/distros have and thus must rely on some 3rd party sites for full multimedia support.
That would be great if an app from flathub could create all the thumbnails that are not supported by default in GNOME, but it is two years old and a last comment is nine months old. Thank you for the link.