A media reproducing device comprises a media data output element operable to output media data stored on a storage medium to a media data presentation unit. The media reproducing device further includes a receiver operable to receive a sequence of video images, and a user detector operable to detect, by analysis of the sequence of video images, whether a user is attending to a presentation of the media data by the media data presentation unit. The user detector is operable to detect whether the user is attending to the presentation of the media data and to generate motion vector tracks associated with movement of objects within the sequence of received video images. If it detects that the user is not attending to the presentation of the media data, the detector is operable to store a bookmark indicating that the user is not attending to the presentation of the media data.