Apparatus for interactively generating a display signal. The apparatus comprises: a receiver (2) for receiving a broadcast signal (15), the broadcast signal comprising a plurality of datastreams each including image data defining a background object (22 270), and control parameters (28 39); a foreground computer generated imagery (CGI) device (3) for generating a foreground computer generated object (CGO); a mixer (4) for combining the foreground CGO with background object image data to generate the display signal; and interaction means (3) for receiving the control parameters from the receiver, monitoring the position of the foreground CGO, and adapting the display signal with reference to the monitored position of the foreground CGO and the received control parameters.