Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for providing television advertisements while a viewing device is tuning to a channel. In one aspect, a viewing device, in response to receiving a signal to tune to a channel, selects advertisement data for an advertisement from a data storage device storing advertisement data for one or more advertisements, and generates a video signal when tuning to the channel, the video signal generated only for the duration that the viewing device is tuning to the channel and for displaying on the television device, and the video signal causing the advertisement to be displayed on the television device.