Every day, a river of video floods the airwaves, courses through cables and streams over the Internet. Add to that all the films ever made, plus all of the video material created for private use, and you've got an ocean of light and sound. But how can you ever find and retrieve a particular video clip?

With text documents, you can type in a query, and a piece of software finds the matching text strings. Searching video is much tougher. Unless someone has gone back and somehow marked the video data, it's now nearly impossible to find a specific image. A content provider like CNN has more than a hundred thousand hours of tape in its video archive-far too much for any human to view and annotate manually. Now a small but growing number of labs are searching for novel ways to better navigate the video glut.