generates a fmtp line like
a=fmtp:<red payloadtype> <opus payloadtype>/<opus payloadtype>
and matches the incoming redundant payload types against the
send codec one. Offers without an FMTP line will not use RED.
Redundancy levels of 1 (plus main packet ) to 32 are accepted but
this is not wired up to the encoder since the O/A semantic of
RFC 2198 is not clear.
This decreases the chance of a collision with the SATIN codec
which also runs on 48khz (but so far does not specify a channelCount of 2)
BUG=webrtc:11640
Change-Id: I8755e5b1e944d105212f1bbe4f330cf4e0753e67
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/229583
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Reviewed-by: Henrik Lundin <henrik.lundin@webrtc.org>
Commit-Queue: Harald Alvestrand <hta@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#34848}
9d07309426