-b flag not interpreted in FFMpeg

Question

I am trying to loop a file out to two rtp ports via ffmpeg. When I run this command, I get the following error:

Codec AVOption b (set bitrate (in bits/s)) specified for output file #0 (rtp://127.0.0.1:49152) has not been used for any stream. The most likely reason is either wrong type (e.g. a video option with no video streams) or that it is a private option of some encoder which was not actually used for any stream.

Command I used:

ffmpeg -y -re -stream_loop -1 -i ./demovideo.m4v -r 24 -s 1280x720 -c:v libvpx -minrate 3M -maxrate 3M -b:v 3M -c:a libopus -map 0:a:0 -f rtp -c copy rtp://127.0.0.1:49152 -map 0:v:0 -f rtp -c copy rtp://127.0.0.1:49154?pkt_size=1012

I have specified that the b flag indicates video with '-b:v'. What am I missing?

Answer 1

The -c copy after -f rtp overrides the -c:v and -c:a options. Place it before -c:v libvpx in your present command.

See here for how option placement takes effect.