Can't generate thumbnails in Nautilus

Please ensure that the necessary packages are installed by running the following command in the terminal:

sudo apt-get install gstreamer0.10-plugins-bad gstreamer0.10-plugins-base gstreamer0.10-plugins-good gstreamer0.10-plugins-ugly totem libxine1-ffmpeg

Also, please delete the thumbnails that failed to load by running the following command:

rm ~/.thumbnails/fail/gnome-thumbnail-factory/*

In Ubuntu 13.10, the folder changes to: .cache/thumbnails, so you should delete those failed files instead:

rm ~/.cache/thumbnails/fail/gnome-thumbnail-factory/*

I followed the instructions in this forum and it worked perfectly.

Install libxine1-ffmpeg.
sudo apt-get install libxine1-ffmpeg

Then to force nautilus to generate new thumbnails execute
rm -r ~/.thumbnails/fail
rm -r ~/.thumbnails/normal
killall -9 nautilus

These commands will remove (delete) thumbnails from these folders.

Open nautilus again and you should be able to see thumbnails for all your videos.