Alitronika DVS AT88IP, Руководство пользователя

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Forward Error Correction
The Pro-MPEG Forum (association of broadcasters, program-makers, and vendors) approved an open
standard to improve QoS in professional video over IP networks, while keeping interoperability between equipment
manufacturers.
Standard is provided as a set of guidelines and recommendations (Codes of Practice).
Code of Practice #3 describes a Forward Error Correction (FEC) method for protection against errors in delivering
professional MPEG-2 TS data over IP networks. This method implemented in IP adapters, packet errors, out of order
packets, network jitter and delay can be compensated. Such process is done in real-time along with TS over IP
encapsulation.
FEC protection data is calculated and embedded in regular RTP packets with a specific payload type, and relies on
simple XOR arithmetic’s (if F=A
?
B
?
C, then if only A,B,F are present, C can be recovered with C=A
?
B
?
F). A FEC matrix
is generated (cf figure 3) and transmitted on two separate UDP ports, FEC columns on UDP port + 2 and FEC rows on
UDP port + 4.