An information signal (INF) which is transmitted in coded form (CINF) from a signal source (RC) to a signal receiver (4,5) is decoded at the receiver and at the same time marked (MINF) by the introduction of an identification information (ID) which is characteristic of the receiver or its possessor. The signal from a video disc (RC) carrying a coded programme is decoded and marked before it is supplied to a television set (6). Via said identification information a so-called pirate copy is directly traceable to its originator. Thereby a protection against such copying is obtained. A device for the playback of a video disc of this type comprises a decoding and modification unit to which the necessary decoding information and identification information may be supplied from a personal data carrier (ID).