How to animate a solid face in a video In this music video, there are some images of famous artists in the view that are animated and look alive.

http://vimeo.com/109646378



By which technique it can be achieved?
is it a frame-by-frame editing of photos and then apply the resulted 2d animations into the video?
The VFX breakdown is right in the link in the video that you provide. 
They break it down for you in the youtube video.


                
            

Its masking, feathering, desaturation or levels adjustment. If moving they also key it in 3D space so the images scale properly to objects in space.

Very well done piece.