Digital broadcasting system and data processing method

A transmitter comprising:

• a pre-processor for pre-processing first service data comprising audio or video data for a mobile service, the first service data is capable of being transmitted via a same channel as second service data comprising audio or video data for a main service, wherein pre-processing the first service data comprises:
• randomizing the first service data,
• generating a Reed-Solomon (RS) frame through which an RS frame payload including the randomized first service data is RS—Cyclic Redundancy Check (CRC) encoded, wherein the RS frame is separated to a plurality of portions, wherein a size of the RS frame payload is 187 by N bytes, and wherein N is an integer corresponding to a length of each row of the RS frame payload,
• forming data groups of the first service data, wherein each data group includes signaling information, a plurality of known data sequences that have pre-determined values, one of the plurality of portions, second service data place holders, RS parity data place holders, and MPEG header data place holders, and wherein the signaling information includes information indicating a number of the data groups to be transmitted during a transmission frame, and
• removing the second service data place holders and the RS parity data place holders and replacing the MPEG header data place holders with MPEG header data to output first service data packets;
• a multiplexer for multiplexing the first service data packets and second service data packets, wherein the second service data packets include the second service data;
• a randomizer for randomizing the multiplexed second service data packets and the MPEG header data in the multiplexed first service data packets;
• and
• a transmission unit for transmitting a broadcast signal including:
• the first service data packets including the randomized MPEG header data, and
• the randomized second service data packets,
• wherein a parade of the formed data groups is transmitted during slots in the broadcast signal, the slots being basic time periods for multiplexing the first service data and the second service data.

A method of processing broadcast data in a receiver, the method comprising:

• receiving a broadcast signal that includes broadcast service data for a service, wherein the broadcast service data is encoded to add parity data, encoded at a code rate, and then block interleaved based on an interleaving pattern in an interleaving unit having a size of L by a transmitter, wherein L is an integer greater than 2, wherein, when a size of a block including the broadcast service data is smaller than the size of L, the interleaving unit includes the broadcast service data and dummy data, wherein the dummy data are not transmitted to the receiver, wherein the broadcast signal further includes service signaling information and transmission parameter data, wherein the service signaling information includes channel information for the service, and wherein the transmission parameter data include information related to a number of the parity data;
• demodulating the broadcast signal;
• first decoding the broadcast service data in the demodulated broadcast signal;
• second decoding the first-decoded broadcast service data;
• and
• derandomizing the second-decoded broadcast service data.

A method of processing broadcast data in a transmitter, the method comprising:

• randomizing broadcast service data for a service;
• first encoding the randomized broadcast service data to add parity data;
• second encoding the first-encoded broadcast service data at a code rate;
• block interleaving the second-encoded broadcast service data based on an interleaving pattern in an interleaving unit having a size of L, wherein L is an integer greater than 2, wherein, when a size of a block including the broadcast service data is smaller than the size of L, the interleaving unit includes the broadcast service data and dummy data, and wherein the dummy data are not transmitted to a receiver;
• convolutional interleaving the block-interleaved broadcast service data;
• and
• modulate a broadcast signal that includes the convolutional interleaved broadcast service data,
• wherein the broadcast signal further includes service signaling information and transmission parameter data,
• wherein the service signaling information includes channel information for the service, and
• wherein the transmission parameter data includes information related to a number of the parity data.