on my wonderful Smart TV LG I've discovered that it creates tn3 files for video's thumbnails (divx, mkv and so on).

I don't like the frame it choose, I think that for my 4 years old daughter should be better to see a specific frame that represent the movie.

Is there a way to edit a tn3 file? I've found free software to convert them in jpg or png files but nothing to convert them back!

Thanks in advance