Well, I don't know much about valgrind, but I tried some further debugging. In SDPGenerate (rtp.c, line ~721): if( p_sys->es[0]->listen_fd != NULL ) getsockname( p_sys->es[0]->listen_fd[0], (struct sockaddr *)&dst, &dstlen ); else getpeername( p_sys->es[0]->sinkv[0].rtp_fd, (struct sockaddr ...