[FFmpeg-user] broadcast multicast stream problems

Andy Smith a.smith at ldex.co.uk
Wed Feb 27 18:27:32 EET 2019

Hi list, 

  I have a requirement to effectively relay a stream to a multicast IP.
The source is an HTTP address streaming 1x video (H264) and 1x audio
(A53 stereo). The idea would be to relay this unmodified to a multicast
IP. I've tried the following: 

ffmpeg -re -y -i -c copy -f mpegts

When I try and connect to the mulitcast stream with VLC player I get an
error about "SDP required: 

A description in SDP format is required to receive the RTP stream". 

If I use rtsp instead of mpegts/udp it bombs out with the error "Could
not write header for output file #0 (incorrect codec parameters ?):
Network is unreachable".

But I'm unsure if its possible to add an SDP description, or even if its
possible to relay this video stream at all via ffmpeg. 

Off topic, I have been able to do this with vlc command line, but its
unreliable, stops and starts, and just plain doesn't work when I try and
run multiple streams. 

I don't have any experience really with multicast and particularly
ffmpeg so I may be getting this all wrong, any suggestions gratefully

thanks, Andy.

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