Broadcast segment recognition systems and methods are provided in which a signature representing a monitored broadcast segment is compared with broadcast segment signatures in a data base representing known broadcast segments to determine whether a match exists. Criteria for determining the validity of such a match are provided. In one aspect, signatures representing audio broadcast signals are formed by comparing temporally displaced portions of respective frequency band values within plural frequency bands of the broadcast audio signal. Systems and methods are provided for producing signatures representing intervals of a video signal which compensate for shifts in an edge of a picture represented by the video signal. In addition, signatures characterizing respective intervals of a broadcast signal exhibiting correlation are produced by generating a difference vector for each respective interval and carrying out vector transformations of the different vectors to reduce such correlation. Moreover, signatures characterizing intervals of a video signal are produced with corresponding mask words representing reliability of values comprising the signature. Mask words of first and second signatures thus formed representing different portions of the video signal displaced from one another are compared to establish the values of the mask word.