How to use blender with movies?

How can i import a file from a video made with a camera into blender to manipulate and add effects? Is it possible?

I want to be able to add blood effects and things like that.

Thanks

You can use the compsoite nodes for that. Just add an “Image” input node, set the number of frames to match what’s in the movie, and make sure that “auto” is set to update frames as you move through the timeline. Then you can create the blood in 3D and use the renderlayer and alpha over nodes to composite it. Of course, if the camera is moving, you’ll probably need to match move the footage with something like Voodoo or Icarus, first.