1. A method of processing an interactive service at a receiver, the method comprising: receiving an uncompressed audio content or an uncompressed video content from an external decoding unit; extracting signatures from frames of the received content; sending the extracted signatures to an ACR (Auto Content Recognition) server, to be checked against a database of signatures of frames in order to recognize the frames represented by the signatures, wherein the frames represented by the signatures are identified by the ACR server; receiving a time base trigger from the ACR server, wherein the type of trigger is decided by the ACR server based on the frames represented by the signatures, wherein the time base trigger establishes a time base for activations of events, wherein the time base is synchronized with the frames, and retrieving an application parameter table using information in the time base trigger, wherein the application parameter table includes information about at least one of applications, wherein the information about at least one of applications include first IDs (identifiers) identifying each of the applications, and information about at least one of the events, wherein the information about at least one of the events include second IDs identifying each of the events, and information about at least one of data to be used for the corresponding event, wherein the information about at least one of data include third IDs identifying each of the data, wherein the retrieving an application parameter table further includes, receiving an activation message table along with the application parameter table, wherein the activation message table includes activation messages for activating the events at activation times relative to the established time base, wherein each of the activation messages include first attributes, second attributes, third attributes and timing information, wherein the first attribute matches the first ID to identify the application targeted by the activation message, wherein the second attribute matches the second ID to identify the event targeted by the activation message, wherein the timing information indicates start of time period for the event targeted by the activation message, and wherein the third attribute matches the third ID to identify the data to be used for the event targeted by the activation message.