The effect i want achieve looks like this where there's an image moving in space with particles (dust, grain, dirt, scratches) moving over them.
The Video is here: https://www.youtube.com/watch?v=altvY5rt6oc
So far I've got stock footage of dust particles but I don't know how to find out if it has an alpha channel and whether one is needed to achieve the effect?
I believe I would set up the scene in the 3D view and then overlay the footage over my images using the compositor. But as i'm still fairly new to the compositor i'm not sure if it's possible and was wondering if anyone knew how to achieve the effect?
I'll experiment and put down what my experimentation with the compositor results in later on today.
I'll probably ask another question on how to achieve the image distortion thats used as well which ill link to this question.
Many thanks to anyone who helps me out.