[FFmpeg-user] UDP unicast & multicast output

[Anacelia Sarlo]

Hello,
      I'am receiving a live stream and I want to copy 2 bit streams (video
H.264 & audio AAC)  and re stream them with mpegts format to an udp
multicast output.
With an udp unicast output it works ok, but when I try with an udp
multicast one, I see the on the ffmpeg console that the rate start to down
and the stream begin
to cut off.
My doubt is how ffmpeg works with udp unicast and multicast, and what could
be wrong with my  multicast example?
I'am attaching both commands.

UDP unicast output
ffmpeg -re -y -i $stream -map 0:4 -map 0:5 -rtbufsize 1G -c copy -f mpegts
-mpegts_pmt_start_pid 66 -streamid 1:71 -streamid 0:70 udp://
192.168.1.109:1234?pkt_size=1316  works OK!

UDP multicast output
ffmpeg -re -y -i $stream -map 0:4 -map 0:5 -rtbufsize 1G -c copy -f mpegts
-mpegts_pmt_start_pid 66 -streamid 1:71 -streamid 0:70 udp://
224.1.1.1:1234?pkt_size=1316 video cut off!

Thanks a lot for your suggestions.
Ana