scope:

Abstract

This document defines new RTP payload formats for the Forward Error Correction (FEC) packets that are generated by the non-interleaved and interleaved parity codes from source media encapsulated in RTP. These parity codes are systematic codes (Flexible FEC, or "FLEX FEC"), where a number of FEC repair packets are generated from a set of source packets from one or more source RTP streams. These FEC repair packets are sent in a redundancy RTP stream separate from the source RTP stream(s) that carries the source packets. RTP source packets that were lost in transmission can be reconstructed using the source and repair packets that were received. The non-interleaved and interleaved parity codes that are defined in this specification offer a good protection against random and bursty packet losses, respectively, at a cost of complexity. The RTP payload formats that are defined in this document address scalability issues experienced with the earlier specifications and offer several improvements. Due to these changes, the new payload formats are not backward compatible with earlier specifications; however, endpoints that do not implement this specification can still work by simply ignoring the FEC repair packets.