Send information of a video through udp

[Pierre Bourré]

Hi,

I have two pipelines, one which encodes a video and sends the stream via
udp, the other one which receives this stream, and displays it.

gst-launch-1.0 filesrc location=example.mp4 ! decodebin !
myplugin_emit_info ! nvh264enc ! rtph264pay ! udpsink port=5000 
host=127.0.0.1 async=false

and

gst-launch-1.0 udpsrc port=5000 ! "application/x-rtp,
media=(string)video, encoding-name=(string)H264, payload=(int)96" !
rtph264depay ! decodebin ! myplugin_receive_info ! ximagesink

I'd like to send information (regions of interest in the image for
example) between these two pipelines. I tried to use
gst_buffer_add_meta() to send these information, but the encoders (here
nvh264enc, but I tried with x264enc, nvh265enc, vp8enc...) remove these
metadata, therefore I can't use them in my second pipeline.

Is there something that I am missing to exchange information between
pipelines? How can I achieve this result with or without GstMeta?

Thank you in advance for your help!

Pierre