Our approach locates the temporal positions of tags in videos at the keyframe level.

We deal with a scenario in which there is no pre-defined set of tags.

We report experiments about the use of different web sources (Flickr, Google, Bing).

We show state-of-the-art results on DUT-WEBV, a large dataset of YouTube videos.

We show results in a real-world scenario to perform open vocabulary tag annotation.