A computer system in which augmentation content can be provided to a client device. A receiver is provided in a server for receiving a live television signal. A matching engine can then identify a segment of television, based on fingerprinting techniques and can determine a time delay between the start time of the segment of television and its identification. A content retrieval unit can then select augmentation content based on the identified segment of television and the time delay, and this can be output to a client device. In this way the augmentation content can be selected so that it maintains synchronisation with live television.