Prevent Nautilus from generating thumbnails for video files larger than 5 MB?

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http://askubuntu.com – If I set in Nautilus preferences that it should generate thumbnail previews only for files larger than 10 MB, then this only works for pictures. Nautilus still keeps generating thumbnails for videos and pdf files. Even if a video file is 500 MB. It should only generate thumbnails for video files less than 10 MB as set in the preferences. Same goes for pdf. I have many pdf files that are larger than 50 MB. I don't want Nautilus to generate thumbnails for these, only for small sized pdf. How can I make Nautilus to obey the Previews preferences? Nautilus 3.4.2 Ubuntu 12.04.1, 64bit (HowTos)