31. The method recited in claim 28 wherein the signal to be identified includes a video signal, and wherein the step of extracting the feature string includes the steps of detecting predetermined events in the video signal and determining the time intervals between detected predetermined events to generate the feature string.
31. The method recited in claim 28 wherein the signal to be identified includes a video signal, and wherein the step of extracting the feature string includes the steps of detecting predetermined events in the video signal and determining the time intervals between detected predetermined events to generate the feature string. 40. The method recited in claim 31 wherein the step of detecting predetermined events includes the steps of monitoring the video envelopes of two frames, obtaining a predetermined number of samples from each envelope and comparing the magnitudes of counterpart samples to obtain a difference in counterpart samples, taking the average of the differences, and indicating a detected predetermined event whenever the average exceeds a predetermined level.