Method for transmitting broadcast signals and method for receiving broadcast signals

A digital receiving apparatus for processing a content, the digital receiving apparatus comprising:

• a receiver configured to receive an uncompressed audio or video content from an external device;
• a processor configured to obtain a watermark message by re-assembling watermark blocks from the uncompressed audio or video content,
• wherein each of the watermark blocks includes a watermark identification field for identifying the watermark message, a fragment number field related to a number of a current watermark block of the watermark blocks, a last fragment field for specifying a number of a last watermark block of the watermark blocks, and a fragment of the watermark message,
• wherein the watermark message includes first information for a first portion of a uniform resource locator (URL) and second information for a second portion of the URL, and
• wherein the processor is further configured to:
• construct the URL based on the first information and the second information, and
• access a supplementary content based on the URL;
• and
• a display device configured to present the supplementary content.