US Patent 10911824 Methods and apparatus to generate reference signatures

Example apparatus disclosed herein include a signature collector to collect a first signature for media being presented to a plurality of households, a media creditor to credit the media when the first signature matches a reference signature in a reference signature database. The example apparatus also includes a signature thresholder to, when the first signature does not match the reference signature in the reference signature database, determine if the first signature matches an unknown signature in an unknown signature database; increase a count associated with the unknown signature when the first signature matches the unknown signature; and determine when a second signature matches the first signature, the second signature including metadata identifying the media. The example apparatus also includes a signature handler to store a reference signature for the first signature by associating the metadata identifying the media with the first signature when the count of the first signature satisfies a threshold, the reference signature to be stored in the reference signature database.