The present invention relates to a method for dynamic image content replacement in a video stream comprising generating a set of key image data (K) comprising a sequence of at least two different key images (K1, K2), periodically displaying said set of key image data (K) on a physical display, generating at least a first original video stream (O1) of a scene which includes said physical display by recording said scene with a camera, wherein said at least one video stream (O1) comprises key video frames (FK1, FK2), captures synchronously with displaying each of said at least two different key images (K1, K2) of said set of key image data (K) on said physical display, generating a mask area (MA) corresponding to an active area of said physical display visible in said key video frames from differential images (AFK) obtained from consecutive key video frames (FK1, FK2), generating at least one alternative video stream (V) by inserting of alternative image content (I) into the mask area (MA) of an original video stream, and broadcasting at least said at least one alternative video stream.