A method of processing information in a digital receiver connected to an external input source includes receiving uncompressed data of a broadcast service from the external input source, the broadcast service delivered based on either a Real-Time Object Delivery over Unidirectional Transport (ROUTE) protocol or an MPEG Media Transport (MMT) protocol; extracting an audio watermark from the uncompressed data; making a request to a specific server using domain type and server code of the audio watermark to form a first URL; receiving a recovery file including a second URL used to retrieve signaling files needed to access and present a supplementary content; retrieving the signaling files using the second URL in the recovery file; and presenting the supplementary content based on the signaling files. Further, timing information included in the recovery file is used to synchronize the supplementary content with the uncompressed data from the external input source.