I am having exactly the same problems trying to output an sdp file locally. I have followed what instructions and examples I can find exactly, and no sdp file is created.
here is my line (On Vista64):
:sout=#transcode{vcodec=h264,vb=300,scale=0.5,acodec=mp4a,ab=64,channels=2}
:duplicate{dst=display,dst=rtp{dst=xxx.xxx.xxx.xxx,mux=mp4,port=xxxx,port-audio=xxxx,port-video=xxxx,sdp=file://C:/test.sdp}}
tried many dif paths etc, with and without play locally, no luck anybody any ideas where I am going wrong?
Used Quicktime Broadcaster, Wirecast (Mac & PC) without problems (been live streaming for over 3 years), but I cant get an sdp file out of VLC.....