The present invention provides a method of transmitting broadcast signals. The method includes, generating input packets including broadcast content data; generating a link layer packet by using the generated input packets, wherein the link layer packet includes a link layer header and a link layer payload including the generated input packets, wherein the link layer header includes a count field indicating number of the input packets included in the link layer payload, wherein the link layer header further includes a length part, wherein the length part includes a plurality of length fields as many as that the count field indicates, wherein each of the length fields indicates length of the each input packets included in the link layer payload; generating a broadcast signal including the generated link layer packet; and transmitting the broadcast signal.