Encoding system

Abstract

The method of encoding a given recorded signal made up of a host of different frequencies comprises modifying the recorded signal to selectively alter in a known manner a portion of the recorded signal to produce a machine recognizable start code which is generally unperceptible to human recognition when the recorded signal is played in its intended manner. The signal is scanned and immediately after the start code, an identity code is generated based on the particular signal characteristics which collectively are unique to the recorded signal and by means of which the recorded signal can be identified. A recorded signal which has been encoded in accordance with this method has a start code which can be machine recognized during playing of the recorded signal. This recognized start code locates a portion of the signal used to identify the same. Apparatus for carrying out this particular method, both in encoding of the recorded signal and scanning of signals which have been encoded, form part of the present invention. This invention is particularly useful for monitoring of broadcast signals having included therein material covered by copyright.

Dependencies are inferred from the claim text.