A computing system identifies a media stream being received by a client, based on fingerprint matching conducted with query fingerprints generated by the client at a frame rate. The computing system then causes the client to increase the frame rate, in order to facilitate establishment by the computing system of synchronous lock between true time within the media stream and client time according to an clock of the client. The computing system then uses the established synchronous lock as a basis to map a true-time point at which a content revision should be performed in the media stream to a client-time point at which the client should perform the content revision. And the computing system causes the client to perform the content revision at the determined client-time point.