Digital broadcasting system and method of processing data

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

• Reed-Solomon (RS) encoding and Cyclic Redundancy Check (CRC) encoding, by an RS frame encoder, mobile service data to build an RS frame including the mobile service data, dividing the built RS frame into RS frame portions and adding K bytes of dummy data to one of the RS frame portions, wherein K is greater than or equal to zero;
• mapping, by a group formatter, one of the RS frame portions into at least one region of a data group that has a plurality of regions and adding a plurality of known data sequences, signaling information and Moving Picture Experts Group (MPEG) header data place holders to the data group, wherein at least two of the plurality of known data sequences have different lengths and wherein at least two of the plurality of known data sequences are spaced 16 segments apart;
• replacing, by a packet formatter, the MPEG header data place holders with MPEG header data, in order to output mobile service data packets;
• multiplexing, by a multiplexer, the mobile service data packets and main service data packets, the main service data packets including main service data;
• trellis encoding, by a trellis encoding module, data in the multiplexed data packets;
• and
• initializing at least one memory in the trellis encoding module at a start of at least one of the plurality of known data sequences.