How to preview video files in nautilus just like audio files ?

[Pranav Ganorkar <pranavg india gmail com>]

Nautilus is a very good File browser. It has a very good functionality 
of previewing audio files. I want to extend it's previewing capacity to 
video files.Please can anyone tell me how can I make these changes.
By changing the source code or by using extensions?Please tell me more 
information about how to modify the source code to make these changes 
and and then how to replace my existing nautilus with the new functionality.