1. A method comprising: capturing presenter video of a presenter, the presenter video temporally divided into a sequence of media frames, each media frame divided into spatial regions; by a processor: extracting the sequence from the video; analyzing the content on the media frames to determine a set of space and time varying alpha values, wherein the alpha values temporally vary in corresponding spatial regions over the sequence and spatially vary in each media frame over the spatial regions thereof, by assigning each region of each media frame a distinct alpha value equal to: a first value when the region includes presenter video background and a corresponding region of a corresponding media frame of shared digital rich media does not include text, or when the region does not includes a face or facial features of the presenter and the corresponding region includes the text; a second value less than the first value when the region includes the face or the facial features and the corresponding region does not include the text; or a third value less than the first value and greater than the second value when the region include the face or the facial features of the presenter and the corresponding includes the text; performing a compositing operation on the media frames in relation to corresponding media frames of the shared digital rich media to produce combined video frames based on alpha values of the regions of the media frames; and displaying a video of the combined video frames.