66. The improvement recited in claim 50 wherein said signal to be identified includes a video signal and said video signal includes a color signal, wherein the feature string extracting means includes means for determining the time interval between predetermined changes in the color signals.
66. The improvement recited in claim 50 wherein said signal to be identified includes a video signal and said video signal includes a color signal, wherein the feature string extracting means includes means for determining the time interval between predetermined changes in the color signals. 67. The improvement recited in claim 66 wherein the color signal change determining means includes means for comparing a function of the color signal with the average of the color signal and determining the time intervals when the function of the color signal exceeds the average of the color signal and the time intervals when the function of the color signal is less than the average of the color signal to extract the feature string.