how to implement a fake webcam?

I want to play a recorded movie as my webcam? How can i do this , i am a Delphi programmer it's necessary to write a device driver ?

I am waiting for ideas on getting this task done.Thank you!

You'll want to take a look at the Windows Image Acquisition service. At first glance it looks like you're correct. You will probably have to write a user mode driver to do this. Once this is accomplished you should be able to stream your movie through any software that takes advantage of a webcam.

If you want the movie to be accessible to webcam-related APIs and OS features, then yes, you would need to write (or find a thirdp-party) device driver that is usable by multimedia APIs.