Implenting background subtraction

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I am working on project that needs to identify humans completely or partially. I tried using various haar cascade Hod cascades etc but these dont really seem to have the expected results with my project. The thing I want to implement is same as in this video : https://www.youtube.com/watch?v=KRKKektCcok

I have a static background and hence the detection of the foreground will be much more easy with that. I need some clues to start with for implementing something as in the above video.