Google has officially unveiled a prototype video search that scours the closed captioning text of television shows. Results are displayed with a still image of the video, along with snippets of text that contain the search terms. Yahoo, meanwhile, has ramped up video search efforts of its own in response to Google's move.

Still in early beta testing, Google Video has been indexing since December television programming from PBS, Fox News, CSPAN, as well as local San Francisco channels including ABC and NBC. Until licensing is ironed out, users will not able to view the full video clip nor read a transcript of the program.

In the meantime, an "About this show" side panel provides information on when the program airs next.

Not to step on the toes of content owners, Google has also left off contextual text ads from its video search. Down the road, the company sees numerous possible revenue models, including commercials within video clips.

But Google isn't the only search provider that sees opportunity in video. Yahoo has begun promoting its TV and video search on its main Web site after first launching the beta in December.

Taking a slightly different approach from Google, Yahoo currently searches text around video links and metadata attached to the video file. However, Yahoo plans to index closed captioning content from the BBC, Bloomberg and Sky within the next few weeks through a partnership with TVEyes.