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Ever since yesterday, Nautilus stopped showing me thumbnails for new mkv files. It still works for other videos like mp4, avi, flv,...
I'm pretty sure it started happening since the last shared-mime-info update:
[2026-07-03T00:17:02+0200] [ALPM] upgraded shared-mime-info (2.4-3 -> 2.5.1-1)Reverting to 2.4-3 fixes the issue but I'd rather not do that.
From what I checked, the MIME configuration and its link with the thumbnailer seems OK:
[ginko@PC ~]cat /etc/mime.types | grep -i mkv
video/x-matroska mkv
[ginko@PC ~]$ cat /usr/share/thumbnailers/ffmpegthumbnailer.thumbnailer | grep -i matroska
MimeType=video/3gpp;video/3gpp2;video/annodex;video/dv;video/isivideo;video/mj2;video/mp2t;video/mp4;video/mpeg;video/ogg;video/quicktime;video/vnd.avi;video/vnd.mpegurl;video/vnd.radgamettools.bink;video/vnd.radgamettools.smacker;video/vnd.rn-realvideo;video/vnd.vivo;video/vnd.youtube.yt;video/wavelet;video/webm;video/x-anim;video/x-flic;video/x-flv;video/x-javafx;video/x-matroska;video/x-matroska-3d;video/x-mjpeg;video/x-mng;video/x-ms-wmv;video/x-nsv;video/x-ogm+ogg;video/x-sgi-movie;video/x-theora+ogg;application/mxf;application/vnd.ms-asf;application/vnd.rn-realmedia;application/x-matroska;application/ogg;I also tried using the command found in ffmpegthumbnailer.thumbnailer to generate a thumbnail and it works fine
ffmpegthumbnailer -i test.mkv -o test.jpg -fDeleting the whole thumbnail cache in ~/.cache/thumbnails/ and rebooting didn't help. I just don't have thumbnails for any mkv file now.
And I couldn't find any relevant log in the systemd journal.
Does anyone have any clue what might be wrong here?
Last edited by Ginko (2026-07-10 17:05:08)
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Downgrading `shared-mime-info` fixes it. ~
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Quick fix with shared-mime-info 2.5.1-1:
add video/matroska; (with the closing semicolon!) to the end of the MimeType= line in /usr/share/thumbnailers/gst-video-thumbnailer.thumbnailer
quit Nautilus
clear out the thumbnails cache
restart Nautilus
Now all mkv videos have thumbnails again.
sudo sed -i -r 's|^(MimeType=.*)|\1video/matroska;|' /usr/share/thumbnailers/gst-video-thumbnailer.thumbnailer
nautilus -q
rm ~/.cache/thumbnails/{fail/gnome-thumbnail-factory,large,normal}/*The cause is shared-mime-info 2.5 replaced the */x-matroska types with the IANA registered */matroska types and gst-thumbnailers wasn't updated for that yet.
I've submitted an MR to gst-thumbnailers to add them: https://gitlab.gnome.org/GNOME/gst-thum … equests/42 (edit: the MR is merged, so the next gst-thumbnailers release will fix this issue without needing the workaround)
Last edited by jakedane (2026-07-07 14:55:31)
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Quick fix with shared-mime-info 2.5.1-1:
add video/matroska; (with the closing semicolon!) to the end of the MimeType= line in /usr/share/thumbnailers/gst-video-thumbnailer.thumbnailer
quit Nautilus
clear out the thumbnails cache
restart Nautilus
Now all mkv videos have thumbnails again.
sudo sed -i -r 's|^(MimeType=.*)|\1video/matroska;|' /usr/share/thumbnailers/gst-video-thumbnailer.thumbnailer nautilus -q rm ~/.cache/thumbnails/{fail/gnome-thumbnail-factory,large,normal}/*The cause is shared-mime-info 2.5 replaced the */x-matroska types with the IANA registered */matroska types and gst-thumbnailers wasn't updated for that yet.
I've submitted an MR to gst-thumbnailers to add them: https://gitlab.gnome.org/GNOME/gst-thum … equests/42
It's also affecting `thumbler`.
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It's also affecting `thumbler`.
I don't know what that is but I assume the fix will be the same, add the non-x */matroska types to it.
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Quick fix with shared-mime-info 2.5.1-1
Sorry for the late reply but thanks, this fixed it!
I added video/matroska; to ffmpegthumbnailer.thumbnailer since it's the one I'm using and thumbnails are working again.
ffmpegthumbnailer fixed it on their side 5 days ago so its next version should also fix this issue:
https://github.com/dirkvdb/ffmpegthumbn … 5a0c894698
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