A codec comprising a video input (33) for receiving a continuous video stream, an encoder (42) for encoding the video stream to result in an encoded video stream, a video output (37) for transmitting the video stream and switching means (39). The switching means is for switching the encoded video stream during encoding between a first mode, in which the video stream is encoded in accordance with a first encoding format, to a second mode, in which the video stream is encoded in accordance with a second encoding format. The invention also relates to a corresponding codec for decoding the video stream. In another aspect the invention concerns a processor for identifying an outline of a subject within a video image.