Video thumbnailer that can be used by file managershttps://github.com/dirkvdb/ffmpegthumbnailer
This video thumbnailer can be used to create thumbnails for
video files. The thumbnailer uses ffmpeg to decode frames from the
video files, so supported video formats depend on the configuration
flags of ffmpeg.
The project also includes a C/C++ library that can be used by
developers to generate thumbnails in their projects.