The invention relates to a method and apparatus for transmitting and for receiving broadcast signals. The present invention provides a method of transmitting broadcast signals. The method includes, processing input streams into BB (Base Band) frames of PLPs (Physical Layer Pipes), wherein the input streams include a plurality of input packets, wherein each of the input packets include a packet header including information about synchronization of the input streams, wherein the processing input streams into BB frames further includes compressing the packet headers of the input packets in the input streams, generating the BB frames by using the compressed input packets; encoding data of the PLPs; building at least one signal frame by mapping the encoded data of the PLPs; and modulating datain the built signal frame by OFDM (Orthogonal Frequency Division Multiplexing) method and transmitting the broadcast signals having the modulated data.