oRTP - Real-time Transport Protocol library

Features:

* Written in C, works under Linux (and probably any Unix) and Windows
* Implement the RFC3550 (RTP) with a easy to use API with high and low level
  access
* Includes support for multiples profiles, AV profile (RFC3551) being the
  one by default
* Includes a packet scheduler for to send and recv packet "on time",
  according to their timestamp.  Scheduling is optionnal, rtp sessions can
  remain not scheduled
* Supports mutiplexing IO, so that hundreds of RTP sessions can be scheduled
  by a single thread
* Features an adaptive jitter algorithm for a receiver to adapt to the
  clockrate of the sender
* Supports part of RFC2833 for telephone events over RTP
* The API is well documented using doxygen
* Licensed under the Lesser Gnu Public License
* RTCP messages sent periodically since 0.7.0 (compound packet including
  sender report or receiver report + SDES)
* Includes an API to parse incoming RTCP packets

WWW: https://www.linphone.org/technical-corner/ortp.html