US Patent 10129591 Signature retrieval and matching for media monitoring

Methods, apparatus and articles of manufacture for signature retrieval and matching for media monitoring are disclosed. An example apparatus includes a hash table populator to store hash keys of reference signatures included in a reference signature block associated with reference media in entries of a hash table, and store qualifier data in the entry of the hash table, the qualifier data including a timestamp, an offset, and an identifier associated with the reference signature of the hash key. The apparatus further including a block table populator to store a block table key corresponding to the reference signature block in the entry of a block table, the block table key including the timestamp and the identifier, and store the reference signature block, a preceding reference signature block and a subsequent reference signature block in the first entry of the block table. The apparatus further including a signature matcher to access the hash table and the block table to retrieve candidate reference signatures to compare with site signatures to identify the monitored media.