How to get reference background image using temporal median filtering?

I am working for moving object detection from video sequences and want to get first the reference background image.i am using temporal median filtering method.i am attaching a code on which i am working but not finding the resultd it is showing error.please help me with this.

[John D'Errico]

We don't just provide code for your homework. That is not the purpose of this site. You need to make an effort.