Google (and YouTube for that matter)  searches video using closed captions, user-provided tags, or text embedded in web pages. Based on visual evidence obtained from Google tech talks by Alex Hauptmann and John Smith I have reason to believe that concept-based video retrieval, i.e. searching based on the visual content, is receiving more and more attention at Google. The video frame on the left shows the audience at the TechTalk by Alex on March 1st 2006, while the frame on the right shows the audience at John’s talk on October 25, 2007. Note the audience increase. I wonder how many people will attend the next Google TechTalk on this topic ;)

Concept-based video search receives more an more attention at Google. On the left the number of attendees during a talk on the topic in early 2006, on the right the number of attendees during a talk in late 2007.