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. 35. The method recited in claim 31 wherein the step of detecting predetermined events includes the step of monitoring the video envelopes of at least one field of two frames.