This codec offer interface provides a method of signalling for RTCP extended reports, documented by RTP Control Protocol Extended Reports (RTCP XR) (RFC 3611). CMs should ignore all RTCP Extended Report parameters that are not listed in this spec at the time of implementation. More parameters can be added to the spec as required.
For more details on what RTCP extended reports can do and how to use them, one should refer to RFC 3611.