Evaluating sources and strategies for learning video concepts from social media
Learning video concept detectors from social media sources, such as Flickr images and YouTube videos, has the potential to address a wide variety of concept queries for video search. While the potential has been recognized by many, and progress on the topic has been impressive, we argue that two key questions, i.e., What visual tagging source is most suited for selecting positive training examples to learn video concepts? and What strategy should be used for selecting positive examples from tagged sources?, remain open. As an initial attempt to answer the two questions, we conduct an experimental study using a video search engine which is capable of learning concept detectors from social media, be it socially tagged videos or socially tagged images. Within the video search engine we investigate six strategies of positive examples selection. The performance is evaluated on the challenging TRECVID benchmark 2011 with 400 hours of Internet videos. The new experiments lead to novel and nontrivial findings: (1) tagged images are a better source for learning video concepts from the web, (2) selecting tag relevant examples as positives for learning video concepts is always beneficial and it can be done automatically and (3) the best source and strategy compare favorably against several present-day methods.