An encoding data processing apparatus generates a video material item marked copy by embedding a payload data word into the video material item. The video material item includes plural video frames. A code word generator generates a water mark code word from the payload data word and reads data representing the water mark code word into a shuffle data store. A shuffle processor generates pseudo randomly at least one address within an address space of the shuffle data store for each video frame and reads data representing part or parts of the water mark code word out from the data store at locations identified by the pseudo randomly generated address. A data embedding processor receives the video material item and embeds the data representing the part or parts of the water mark code word read out from the shuffle data store for each frame into a corresponding frame of the video material item.