US Patent 7421723 Detection of media links in broadcast signals

A detection apparatus includes a tuner tuned to the program and a meter coupled to the tuner and arranged to detect content ancillary information from the program tuned by the tuner. The content ancillary information may be a media link, closed captioning information, or the like. The meter may also be arranged to extract a broadcast signature from the program. A comparator compares the broadcast signature to a reference signature selected from a library of reference signatures based upon the content ancillary information. Broadcast signatures from unknown programs may be clustered at least partially on the basis of the content ancillary information.