Although streaming over RTP is a common requiement, the number of libraries implementing RTP in a generic, reusable, manner is limited. There are one or two good C++ implementations, but the current C implementations all seem to have severe weaknesses. Also, none currently merge related streaming activities, like UDPTL (the commonest transport for T.38 FoIP). Vale is being developed to fill this gap.
The source code for Vale may be found here. More frequent snapshots of the source code may be found here.