In an embodiment, a system includes a receiver for receiving a video signal over a lossy medium and a decoder coupled to the receiver and arranged to decode the video signal for output to a display. The decoder includes a concealment module for regenerating a portion of image data lost from the video signal over said medium, by interpolating or extrapolating from other image data of the video signal received over the medium. The decoder comprises a controller configured to select, based on a measure of loss effect estimated for the portion of image data, whether (i) to apply the concealment module to regenerate the portion of image data, or alternatively (ii) to freeze preceding image data of the video signal in place of the portion of image data.