Dynamic video overlays

A client device accesses a video input stream from an intermediate device for display. The client device analyzes the video input stream to determine that the video input stream matches a template corresponding to a screen portion. Based on the video input stream matching the template, a video output stream is generated and caused to be presented on a display. In some example embodiments, the analysis is performed while the client device is replacing video content received from a content source via the intermediate device. For example, commercials transmitted from a national content provider to a smart TV via a set-top box may be replaced with targeted commercials. During the replacement, menus generated by the set-top box may be detected and the replacement video altered by the smart TV to include the menus.