A telecommunications system including a network; a plurality of user devices coupled to the network; a multipoint control unit coupled to the network and configured to supervise multipoint conferencing among the plurality of user devices, the multipoint control unit including a presentation mixer, the presentation mixer configured to remove one or more backgrounds from a presentation and mix a live video feed into the presentation as a substitute background; and a screen for displaying a resulting mixed presentation such that a full area of the screen is used to display the mixed presentation. In some embodiments, the presentation mixer is further configured to adjust a level of transparency of the substitute background.