Fix regression when used in combination with new flvmux which was ported to GstAggregator, and which sends plain video/x-flv caps before sending full caps that include streamheaders.
rtmpsrc/sink: These plugins require librtmp from http://rtmpdump.mplayerhq.hu/ You have to build librtmp with -fPIC to be able to use it with the GStreamer plugin: make XCFLAGS="-fPIC"