Uninstalled builds using rtp would fail with:
stage/usr/local/lib/x86_64-linux-gnu/libgstsdp-1.0.so: undefined reference to `gst_rtp_payload_info_for_pt'
Name: GStreamer SDP Library, Uninstalled
Description: SDP helper functions, uninstalled
Version: @VERSION@
-Requires: glib-2.0
+Requires: glib-2.0 gstreamer-@GST_API_VERSION@ gstreamer-rtp-@GST_API_VERSION@
Requires.private: gio-2.0
Libs: -L${libdir} -lgstsdp-@GST_API_VERSION@
Cflags: -I@abs_top_srcdir@/gst-libs -I@abs_top_builddir@/gst-libs
Name: GStreamer SDP Library
Description: SDP helper functions
-Requires: glib-2.0
+Requires: glib-2.0 gstreamer-@GST_API_VERSION@ gstreamer-rtp-@GST_API_VERSION@
Requires.private: gio-2.0
Version: @VERSION@
Libs: -L${libdir} -lgstsdp-@GST_API_VERSION@