Apparatus and method for communication in broadcast system

A transmitting device of a broadcast system, comprising:

• a transmitter configured to transmit a transmission packet to an external device for a broadcast service;
• and
• at least one processor connected with the transmitter and configured to generate the transmission packet for the broadcast service,
• wherein the at least one processor is configured to:
• generate a source symbol block having plurality of source symbols using a source packet block having a plurality of source packets by one generation mode of a plurality of generation modes (ssbg_mode #0, #1, #2),
• generate a repair symbol block for the generated source symbol block by one forward error correction (FEC) scheme of a plurality of forward FEC schemes (FEC payload ID mode 0, FEC payload ID mode 1),
• generate a source packet by the plurality of source packets, and
• generate the repair packet in which length repair data and a repair FEC payload identifier (ID) are included in response to an occurrence of a discontinuity of a packet sequence number, and a first FEC scheme (FEC payload ID mode 1) being applied to generate the repair symbol block.

A method of restoring a transmission packet by a receiving device in a broadcast system, the method comprising:

• receiving a source packet including a plurality of source packets and a repair packet including a repair symbol block;
• identifying whether a packet sequence number is disconnected and a fist FEC scheme (FEC payload ID mode 1) among a plurality of FEC schemes (FEC payload ID mode 0, FEC payload ID mode 1) is applied, to generate the repair symbol block based on a plurality of flags included in a repair forward error correction (FEC) payload identifier (ID) of the repair packet;
• decoding length repair data of the repair packet in response to an occurrence of the packet sequence number and the first FEC scheme (FEC payload ID mode 1) being applied;
• and
• restoring a missing transmission packet using the decoded length repair data,
• wherein the plurality of flags include a first flag (D:
• discontinuity flag) indicating that the discontinuity of the packet sequence number has occurred, a second flag (I) indicating whether the length repair data is included in the repair packet, a third flag (F:
• FEC_parameter_flag) indicating whether the same FEC code is used to generate the repair symbol block and the length repair data, and a fourth flag (N:
• num_LRS_flag) indicating whether a number of repair symbols included in the length repair data is the same as the number of repair symbols included in the repair packet, and
• wherein the repair FEC payload identifier (ID) further includes information about a length configured considering the first to fourth flags.

A receiving device of a broadcast system, comprising:

• a receiver configured to receive a source packet including a plurality of source packets and a repair packet including a repair symbol block;
• and
• at least one processor connected with the receiver and configured to repair a source packet received through the receiver,
• wherein the at least one processor is configured to:
• identify whether a packet sequence number is disconnected and a fist FEC scheme (FEC payload ID mode 1) among a plurality of FEC schemes (FEC payload ID mode 0, FEC payload ID mode 1) is applied, to generate the repair symbol block based on a plurality of flags included in a repair forward error correction (FEC) payload identifier (ID) of the repair packet,
• decode length repair data of the repair packet in response to an occurrence of the packet sequence number and the first FEC scheme (FEC payload ID mode 1) being applied, and
• repair a missing transmission packet using the decoded length repair data,
• wherein the plurality of flags include a first flag (D:
• discontinuity flag) indicating that the discontinuity of the packet sequence number has occurred, a second flag (I) indicating whether the length repair data is included in the repair packet, a third flag (F:
• FEC_parameter_flag) indicating whether the same FEC code is used to generate the repair symbol block and the length repair data, and a fourth flag (N:
• num_LRS_flag) indicating whether a number of repair symbols included in the length repair data is the same as the number of repair symbols included in the repair packet, and
• wherein the repair FEC payload identifier (ID) further includes information about a length configured considering the first to fourth flags.