1. A system comprising: a data processing apparatus; and a computer storage medium encoded with a computer program, the program comprising instructions that when executed by the data processing apparatus cause the data processing apparatus to perform operations comprising: receiving a digital video comprising video data; processing the video data to detect features indicative of a human face in the digital video; determining, from the video data, a first frame, in which the features indicative of the human face are detected in the digital video; determining first timestamp data corresponding to the first frame; determining, from the video data, a second frame, in which the features indicative of the human face are detected in the digital video; determining second timestamp data corresponding to the second frame; generating an identifier corresponding to the human face; generating a data set comprising the identifier, the first timestamp data, and the second timestamp data; appending the data set to the video data to provide annotated video data; and displaying an indicator that indicates a location of the human face in the digital video while the digital video is playing, wherein the indicator is an annotation associated with the human face, and wherein the indicator includes the identifier of the human face.