A simple video thumbnailer that uses mpv, primarily intended to be used by a file browser. If you use mpv as your video player and are happy with its playback, you'll likely be happy with mpv-thumbnailer's thumbnails. File format support should be good and aspect ratio errors rare.
mpv-thumbnailer includes and installs a thumbnailer definition file that works with GNOME's Nautilus. Support for other platforms or file browsers should be easy to add.
Usage: mpv-thumbnailer -i VIDEO -o THUMBNAIL [-s SIZE]
VIDEO is the input file to generate a thumbnail from and THUMBNAIL is
the output image file to write. SIZE is optional and defaults to 128.
mpv-thumbnailer requires mpv and ImageMagick.