1. A digital content encoder operable to encode a temporal sequence of digital data, comprising: a coarse digital fingerprint generator operable to generate a coarse digital fingerprint characterising the digital data in an interval of the temporal sequence; a fine digital fingerprint generator operable to generate a plurality of fine digital fingerprints for the interval, each fine digital fingerprint characterising the digital data in a respective sub-interval of the interval; and an encoder that selects whether or not to compress only the fine digital fingerprints, wherein the compression of the fine digital fingerprints is carried out by computing a modulo 3 difference between the fine digital fingerprints and a temporal neighbor fine digital fingerprint for the interval to generate a prediction difference matrix, column scanning the prediction difference matrix to form a vector, and encoding the vector.