Methods and apparatus to generate reference signatures

A method comprising:

• collecting a signature, wherein the signature is associated with a presentation of unidentified media being presented to a plurality of locations;
• determining that the signature does not match reference signatures in a first signature database;
• identifying, based on the determining that the signature does not match the reference signatures in the first signature database, that the signature is associated with metadata,
• wherein the metadata includes media identifying information related to the unidentified media;
• determining that the signature matches a preliminary signature in a second signature database, different than the first signature database;
• increasing, based on the determining that the signature matches the preliminary signature in the second signature database, a count associated with the preliminary signature;
• determining that the count associated with the preliminary signature satisfies a count threshold;
• and
• storing, based on the determining that the count satisfies the count threshold, the preliminary signature as a new reference signature in the first signature database.

A non-transitory computer-readable storage medium, having stored thereon program instructions that, upon execution by a processor, cause performance of a set of operations comprising:

• collecting a signature, wherein the signature is associated with a presentation of unidentified media being presented to a plurality of locations;
• determining that the signature does not match reference signatures in a first signature database;
• identifying, based on the determining that the signature does not match the reference signatures in the first signature database, that the signature is associated with metadata,
• wherein the metadata includes media identifying information related to the unidentified media;
• determining that the signature matches another signature in a second signature database, different than the first signature database;
• increasing, based on the determining that the signature matches the other signature in the second signature database, a count associated with the other signature;
• determining that the count associated with the other signature satisfies a count threshold;
• and
• storing, based on the determining that the count satisfies the count threshold, the other signature as a new reference signature in the first signature database.