A method comprising: generating query fingerprints of frames of a media stream being received by a client , wherein the query fingerprints are generated at a frame rate, the frame rate defining a quantity of frames per unit time for which query fingerprints are generated; providing the generated query fingerprints for use to identify the media stream being received by the client based on comparison with reference fingerprints representing a known media stream; after identification of the media stream being received by the client , increasing the frame rate of generating the query fingerprints; providing the query fingerprints generated at the increased frame rate, for use to establish a time mapping between (i) true-time defined along a timeline within the known media stream and (ii) client-time defined according to a clock of the client , wherein the time mapping is established by detecting at least one match between the query fingerprints generated by the client at the increased frame rate and the reference fingerprints of the known media stream, and correlating a true-time timestamp of the at least one match with a client-time timestamp of the at least one match; and performing , at a specific client-time point, a content revision of the media stream being received by the client , wherein the specific client-time point is determined based on the established time mapping, and wherein determining the specific client-time point based on the established time mapping includes using the established time mapping as a basis to map a predefined true-time point at which the content revision should be performed in the known media stream to the client-time point at which the client should perform the content revision in the media stream being received by the client . generating query fingerprints of frames of a media stream being received by a client , wherein the query fingerprints are generated at a frame rate, the frame rate defining a quantity of frames per unit time for which query fingerprints are generated; providing the generated query fingerprints for use to identify the media stream being received by the client based on comparison with reference fingerprints representing a known media stream; after identification of the media stream being received by the client , increasing the frame rate of generating the query fingerprints; providing the query fingerprints generated at the increased frame rate, for use to establish a time mapping between (i) true-time defined along a timeline within the known media stream and (ii) client-time defined according to a clock of the client , wherein the time mapping is established by detecting at least one match between the query fingerprints generated by the client at the increased frame rate and the reference fingerprints of the known media stream, and correlating a true-time timestamp of the at least one match with a client-time timestamp of the at least one match; and performing , at a specific client-time point, a content revision of the media stream being received by the client , wherein the specific client-time point is determined based on the established time mapping, and wherein determining the specific client-time point based on the established time mapping includes using the established time mapping as a basis to map a predefined true-time point at which the content revision should be performed in the known media stream to the client-time point at which the client should perform the content revision in the media stream being received by the client . <EOS>