A data structure, such as a digital television signal, includes (a) a video stream representing a picture and (b) auxiliary information, such as a closed caption stream. In one embodiment, the picture has an inset window representative of a reduced version of the picture properly overlaid by the auxiliary information. In another embodiment, the data structure has two or more auxiliary information streams, and the picture is used to independently test the auxiliary information processing of each of the auxiliary information streams.