TS packet grooming
View Patent ↗Received data packets are groomed to improve performance of MPEG-2 transport stream packet in a digital video broadcasting system. Multitude of crosschecking techniques are applied to ensure that crucial pieces of information such as the packet identifier (PID) field, the continuity counter (CC) field, table ID, section length, IP header checksum, table and frame boundaries, application data table size are corrected if necessary.
1. A method of grooming transport stream (TS) packets in a receiver of a digital video broadcasting (DVB) system, the method comprising:
parsing a header field of a received TS packet;
comparing a packet identifier (PID) field of the received TS packet with a selected packet identifier (PID) value;
comparing a continuity counter (CC) field of the received TS packet with an expected CC value;
modifying the CC field of the received TS packet if the PID field of the received TS packet matches the selected PID value and the CC field of the received TS packet does not match the expected CC value;
changing the PID field of the received TS packet to the selected PID value if the PID field of the received TS packet does not match the selected PID value and the CC field of the received TS packet matches the expected CC value ; and
forwarding the received TS packet to a processing module if the PID field of the received TS packet matches the selected PID value and the CC field of the received TS packet matches the expected CC value.
2. The method of claim 1 , wherein the processing module is a multi-protocol encapsulation forward error correction decoder configured to process a Reed-Solomon forward error correcting (FEC) decoding function in accordance with an MPEG-2 standard.
3. The method of claim 1 further comprising:
comparing an adaptation field control of the received TS packet with a predetermined adaptation field control pattern; and
modifying an adaptation field length if the PID field of the received TS packet matches the selected PID value and the adaptation field control of the received TS packet matches the predetermined adaptation field control pattern.
4. The method of claim 3 further comprising:
checking a payload unit start indicator (PUSI) field of the received TS packet;
resetting the PUSI field if the PID field of the received TS packet matches the selected PID value and the PUSI field of the received TS packet is equal to unity; and
retaining the PUSI field of the received TS packet if the PID field of the received TS packet matches the selected PID value and the PUSI field is equal to zero.
5. The method of claim 4 further comprising:
comparing a pointer field of the received TS packet with an expected pointer value;
setting the pointer field of the received TS packet to a minimum length value if the PID field of the received TS packet matches the selected PID value, the PUSI field of the received TS packet is equal to unity, and the pointer field of the received TS packet does not match the expected pointer value ; and
modifying a table ID field of the received TS packet if the PUSI field of the received TS packet is equal to unity and a byte indicated by the pointer field of the received TS packet is not a valid table ID.
6. The method of claim 5 , wherein the minimum length value is the minimum of a residual section length value and the result of the subtraction of the adaptation field length from decimal 183 .
7. The method of claim 5 further comprising:
comparing a section length value of the received TS packet with an IP length value;
checking the validity of an IP checksum;
modifying the section length value to the IP length value if the section length value does not match the IP length value and the IP header checksum is valid; and
retaining the section length value if the section length value matches the IP length value and the IP checksum is valid.
8. The method of claim 7 further comprising:
comparing an address field of the received TS packet with a predetermined address value;
modifying the address field of the received TS packet based on a current location of a section if the address field does not match the predetermined address value; and
modifying a table and/or a frame boundary flag of the received TS packet.
9. The method as in claim 1 wherein if the PID field of the received TS packet matches the selected PID value and the CC field of the received TS packet does not match the expected CC value, the CC field of the received TS packet is changed to a value stored in a shadow counter.
10. A method of grooming transport stream (TS) packets in a receiver of a digital video broadcasting (DVB) system, the method comprising:
parsing a header field of a received TS packet;
comparing a packet identifier (PID) field of the received TS packet with a selected packet identifier (PID) value;
comparing a continuity counter (CC) field of the received TS packet with an expected CC value;
modifying the CC field of the received TS packet if the PID field of the received TS packet matches the selected PID value and the CC field of the received TS packet does not match the expected CC value;
changing the PID field of the received TS packet to the selected PID value if the PID field of the received TS packet does not match the selected PID value and the CC field of the received TS packet matches the expected CC value;
forwarding the received TS packet to a processing module if the PID field of the received TS packet matches the selected PID value and the CC field of the received TS packet matches the expected CC value;
comparing an adaptation field control of the received TS packet with a predetermined adaptation field control pattern;
modifying an adaptation field length if the PID field of the received TS packet matches the selected PID value and the adaptation field control of the received TS packet matches the predetermined adaptation field control pattern;
checking a payload unit start indicator (PUSI) field of the received TS packet;
resetting the PUSI field if the PID field of the received TS packet matches the selected PID value and the PUSI field of the received TS packet is equal to unity;
retaining the PUSI field of the received TS packet if the PID field of the received TS packet matches the selected PID value and the PUSI field is equal to zero;
comparing a pointer field of the received TS packet with an expected pointer value;
setting the pointer field of the received TS packet to a minimum length value if the PID field of the received TS packet matches the selected PID value, the PUSI field of the received TS packet is equal to unity, and the pointer field of the received TS packet does not match the expected pointer value; and
modifying a table ID field of the received TS packet if the PUSI field of the received TS packet is equal to unity and a byte indicated by the pointer field of the received TS packet is not a valid table ID.